Murder or accident: How did Shannan Gilbert die?

Produced by Liza Finley, Taigi Smith, Lincoln Farr, Lisa Freed and Sara Rodriguez

The 18-month search for a missing New Jersey woman finally came to an end this week when police on Long Island, New York, announced the discovery remains believed to be 23-year-old Shannan Gilbert. On Saturday, Dec. 17, 2011, the remains were positively identified as Gilbert. As "48 Hours Mystery" correspondent Erin Moriarty reports, the search for Gilbert uncovered a greater mystery.

This is not the first time that Sheree Gilbert has heard the news that her older sister had been found. The first call came a year ago, when her sister, Shannan, had been missing for seven months. Investigators had found the first body -- wrapped in burlap -- on a secluded stretch of beach.

"The investigator from Suffolk County sits us down and says, 'You know we found a body yesterday and we believe it's your sister," Sherre told "48 Hours Mystery" correspondent Erin Moriarty. "My heart just dropped. I started crying. I couldn't believe it."

As Sherre waited for a positive ID the news got even worse. Three more bodies were found on the same beach; a total of four, all about 500 feet apart, all wrapped in burlap.

"And it's just like an emotional roller coaster," she said. "We keep on hearing, "Oh, could be your sister, it could be your sister. This body, this body. It's really crazy."

Someone was strangling young women and then dumping their bodies just feet from the road. Newspapers soon dubbed him the "Long Island Serial Killer."

"The whole name...the 'Long Island Serial Killer' - It just kind of seems like a movie," Sherre continued. "Something that you watch on TV and, you know, it's not something that would happen to you."

Sherre didn't know it, but the plot was about to take another bizarre twist: None of the four bodies were Shannan.

"My reaction was mixed," she told Moriarty. "I was happy but I was also sad because I'm like, 'Well, gee, where is she then?'"

Now, Suffolk County Police Commissioner Richard Dormer had two mysteries on his hands. Who were the four victims? And where was Shannan Gilbert?

"What do you believe happened to Shannan Gilbert?" Moriarty asked Commissioner Dormer.

"I don't know," he replied. "That's the $64,000 question."

The mystery of Shannan's disappearance began on May 3, 2010. Sherre Gilbert got a phone call from her sister's boyfriend reporting that Shannan hadn't come home in two days.

"Immediately, I started to panic ... I knew when he called me that it was something serious..." she says."I could hear the fear in his voice."

It was the call Sherre and her sister, Sarra, had been dreading ever since learning Shannan, diagnosed with a bipolar disorder and struggling with depression and mood swings, had turned to selling her services online as an escort.

"Were you worried about her just going out on these dates, not knowing anything about the guys?" Moriarty asked Sarra.

"Yeah," she replied. "That's very scary, you know."

"What would she tell you when you would say you were worried about it?"

"She would just say, 'Don't worry, I know what I'm doing.' And she pretty much thought that, you know, it would never happen to her."

The Gilberts say they immediately filed a missing persons report, but with no news, they drove 140 miles from their home in upstate New York to Oak Beach, Long Island, to look for Shannan themselves. By then, she had been missing for eight days.

"We went to all the houses around the area to knock on their doors and just say, 'Hey listen, did you see my sister?'" Sherre said. "We gave them flyers. We went everywhere."

They spoke to a dozen witnesses and homeowners in the area trying to piece together a timeline. They learned that Shannan and her driver had left New York City shortly after midnight on May 1, 2010, and headed to a gated community in Oak Beach, Long Island.

"My sister met the client through Craigslist and went to his house around 2:00 a.m.," Sherre explained. "Her driver dropped her off and she was there for quite a while and then - the client told her to leave, and for some reason, she started to panic."

Shannan's sister believes something awful happened in that house to terrify her. Hysterical and incoherent, the phone records show that Shannan made a panicked 23-minute call to 911.

"She told 911 that she was in fear, that they were going to get her, they were going to kill her," according to Robin Sax, an attorney hired by the family to help with their investigation. "They is the big question. Who are they. Was it someone that was in the home, was it someone that was coming after her. She was undoubtedly in fear for her life and safety.

"She ran...down the road...it's a very dark, dark area...and she went to the first place where there seemed to be lights and help," Sax continues. "And that was Colletti's house."

Colletti is Gus Colletti, a retired insurance fraud investigator and resident of Oak Beach for over 30 years.

"It was like 5:00 in the morning," Colletti recalled. "I was in the bathroom shaving. ...All of a sudden, I heard screaming out here and banging on that door. Yelling, 'Help me, help me, help me.'"

He opened the door. Standing there was a young woman he would later learn was Shannan Gilbert.

"She jumped in and stopped right there," he tells Moriarty. "And I said to her, 'What's the matter?' She wouldn't answer me. She just kept staring at me and going, 'Help me, help me, help me.'"

Colletti says he reached for the phone and dialed 911.

"When I said to her, 'I called the police. Sit down in that chair. They're on their way.' She just looked at me and she ran right out the door," he said.

Colletti said it was then that he noticed an Asian man in his 30s driving a black SUV.

"I could see a car come and stopping, coming a little bit and stopping," he said.

Asked if he thought Shannan was afraid of the man in the SUV, Colletti replied, "She was afraid of somebody."

Colletti said he then noticed that Shannan was hiding underneath the boat in his yard.

"All of a sudden, she took off, out from under the boat...And he took off after her. And I yelled to him to stop. And he didn't and he followed her around that way."

"She runs down the street and seems to vanish into thin air..." said Sax. She says that was around 5:30 a.m. "and police arrive at about 6:00 a.m."

Police Commissioner Dormer disputes that time, but admits there was a delay. Shannan couldn't tell the operator where she was. It took the 911 call from Colletti.

"Now we know where she is. An officer was dispatched," said Dormer.

Gus Colletti was waiting at the gate for the officer when he arrived.

"Did the police seem concerned about the missing -- " Moriarty asked Colletti.

"Not at all."

Asked is she thinks the fact that her sister was an escort influenced the investigation, Sarra told Moriarty, "Yes, I do. I believe they judged her by her profession and not as a person. Not as the missing sister, the missing aunt. They're just, 'Oh, a missing prostitute.'"

"My sister had other dreams, you know," Sherre said. "She wanted to be a singer, an actress. She was pursuing that. And she was also goin' to school to be a writer."

The Gilberts say they badgered the police for seven months before investigators started searching in earnest for the missing 23-year-old. It was a random sweep of a nearby beach in December that turned up the grisly grave site - four young women like Shannan who simply disappeared.

In December of 2010, Suffolk County Police Commissioner Richard Dormer downplayed it, but there was little doubt about what his department was confronting. Four bodies had been discovered. All were young women in their 20s. All were online escorts.

One by one, the bodies were identified, and with each name, came the story of a troubled life cut short.

MELISSA BARTHELEMY: Disappeared July 12, 2009

Lynn Barthelemy's 24-year-old daughter, Melissa, had been missing for a year-and-a-half when the bodies were discovered.

"My fiancé and I were actually watching...but they were televising when - where they found the bodies...And we just looked at each other and we started cryin,'" Lynn recalled. "We had a sinking feeling that it was her. And then the next day when Suffolk's County Police Department contacted us and said that they needed to come to Buffalo and speak to us, we just knew."

Photos: Crime scene and victims

After graduating from beauty school, Melissa moved from her small hometown near Buffalo to New York City to work as a hairdresser.

"I was terrified," Lynn said. "I mean, a big city like that. I'm like, 'they're gonna eat you alive.' But she was of age and all I could say was 'be careful' and call her all the time."

What Lynn didn't know at the time was that Melissa was actually working as an escort. In mid July 2009, after several days with no word from Melissa, Lynn panicked.

"Did she get hurt?" Lynn wondered. "We pull out the phone book, we get on the internet. We start callin' hospitals."

Lynn also contacted the NYPD to file a missing persons report, but she was in for a rude awakening.

"They didn't wanna hear anything," she said. "'She's 24. She's not on any psych meds. She's not missing. She's where she wants to be.' And that happened for three days consecutively."

Even the family's attorney, Steven Cohen, couldn't get police to take notice.

"I contacted them," he said. "And they said, 'She's a hooker. She's a prostitute. She was - she's an escort... We're not going to assign a detective to this."

About a week after Melissa disappeared, her 15-year-old sister, Amanda, got a call from Melissa's phone.

"When Amanda answered the phone, you know, she was so excited," Lynn said. "'Oh my God, Melissa's finally calling me.' And then, there's a guy on the other end."

"And this voice is saying, 'Oh, this isn't Melissa,'" Cohen explained. "...he was soft-spoken and had - a very controlled and comfortable manner of speech, which made his horrific messages all the more devastating and he began to toy with her... And for the very first time, she heard the voice of the killer."

Suffolk County police told "48 Hours" that they believe the caller was, in fact, Melissa's killer.

And the calls didn't stop coming. Eight in total, including one in which the likely killer spoke to Lynn. That time, he claimed he was with the NYPD and wanted to know if she had filed a missing persons report. But mainly he focused on Melissa's little sister and called to terrify her.

"And the killer said some pretty horrible things to Amanda," Cohen told Moriarty. "Sexually explicit things as to what he had done to Melissa, sexually explicit things as to what he was going to do to Amanda."

After the third call, police asked Verizon to tap Amanda's phone.

Authorities were able to trace some of the calls to a handful of busy locations in midtown Manhattan; near the Port Authority, the Empire State Building and Times Square. The caller always hung up before he could be identified. But the police were learning a lot about him based on his voice.

"I believe that he is between - his late 20s and his late 30s," Cohen said. "I've been led to believe by Amanda and by the data that I have that he is a white male."

Much has been made about the caller's familiarity with police investigative techniques. He knew what locations would be difficult to trace and how long he could stay on the phone.

"What about talk that this killer might even be part of law enforcement? Do you believe that?" Moriarty asked Retired New York City homicide Commander Vernon Geberth, who has analyzed more than 300 serial murders in the United States.

"No," he replied. "Anybody who watches television - you're bombarded by forensic programs - you can't turn on the TV anymore without 'CSI,' 'NCIS,' 'Law and Order,' and 'Law and Order: Special Victims, and '48 Hours,' OK? So people are watching and they're learning."

"Do you believe this person could be watching the interview right now and enjoying the attention?"

"Well, yes, because he's not identified. In his position right now, he's in a position of superiority," Geberth replied. "He has beaten the police; no one knows who he is. He's immune. It's almost like feeling invulnerable."

That sense of confidence may have driven the caller to reach out to Amanda one last time on Aug. 26, 2009, with a chilling message.

"And he said, 'Do you know what I did to your sister?' And she said, 'No.' He said, 'Well, I killed Melissa,'" Cohen said. "And he also left one of the conversations with the threat that he knows where Amanda lives and might come after her."

"What kind of person calls the little sister of a victim and says, you know, 'You think you're gonna see your sister again? 'Cause I just killed her,' Moriarty asked Geberth.

"A psychopathic, sexual sadist. They're dangerous, a human predator," he replied.

"All I can say is, he's sick. And he's gonna make a mistake. And we're gonna catch him," said Lynn.

Asked if he believes this man will probably kill again, Cohen said, "Oh, there's no question...he is getting better and better at it. He is very controlled, very calculating in what he does. And he's on a mission."

With each burlap-covered victim found on Gilgo Beach, the police learned more about the serial killer: his habits, his M.O. and his uncanny ability to avoid detection.

AMBER COSTELLO: Disappeared Sept. 2, 2010

"She used to say that she was better off dead..." says Dave Schaller, Amber Costello's roommate and friend. In December 2010, detectives showed up at his door. "I was like, 'You guys found Amber... You found her," he said,

By then, Amber had been missing from their home on Long Island for three months. She lived just 10 miles from the killer's dumping ground. Schaller says the last time he saw Amber she was on her way to meet a client who had responded to her online ad.

Photos: Crime scene and victims

"I walked out the front door with her," Schaller recalled. "I was like, 'Be safe.' She gave me a hug and a kiss...and she left."

But when Amber didn't call or come home, says Schaller, no one in her family even looked for her.

"There's something so sad that Amber lived 27 years, disappears, and nobody reports her missing," remarked Moriarty.

"I think she lived her life as if like she didn't even care about herself..." said Schaller.

Schaller says Amber hated the person she'd become - a drug addict who turned tricks to support her habit.

"She knew what she was doing was just like degrading, just despicable," he said. "She absolutely hated it..."

"It strikes me right away David...predators prey on the weak," noted Moriarty.

"Exactly," Schaller agreed, "like a lion smells a dying gazelle."

Schaller says the client enticed Amber with the promise of big money. "If she was going to stay the night ... she would have walked away with $1,500."

"A lot of money for her," said Moriarty.

"Yeah, that's a lot of money for any of these girls," Schaller replied.

The amount was almost six times Amber's going rate. According to Schaller, the man was persistent, repeatedly calling and cajoling Amber that day.

"It was probably around 3 or 4 times...but she was on the phone with him for a while each time," he said.

Schaller says the caller was so persuasive, Amber - an experienced escort - walked out the door without her purse or even a cell phone.

"She had no cell phone with her that night?" asked Moriarty.

"No... She left it at home."

"She didn't even take her purse?"

"Nothing. This guy, whoever it is, he told these girls something they wanted to hear..." Schaller said. "For him to have gotten her to leave so recklessly... I think this guy got into her head somehow."

Somehow he convinced her to meet him alone - an unusual move for Amber, who normally required clients to come to her.

"Do you think the person she went out with that night is the same person who killed her?" Moriarty asked Schaller.

"There's no doubt in my mind..." he replied. "He wanted to kill her."

MEGAN WATERMAN: Disappeared June 6, 2010

Megan Waterman was last seen leaving a Holiday Inn Express on Long Island in June 2010.

Photos: Crime scene and victims

Significantly, this is the same Holiday Inn where a client asked Amber Costello to meet him just few weeks before her death. She refused, but Megan, who usually had someone accompany her on calls, let down her guard and went out into the night alone.

Megan Waterman was just 22 when she was murdered, leaving behind a 4-year-old daughter.

"The world lost an awesome girl, a wonderful, wonderful mom, a friend..." said Megan's mother, Lorraine Ela, who has a message for the killer:

"I want to know why you took my daughter... Why would you hurt a human being? You need to turn yourself in because you will be caught...and you will be caught soon."

MAUREEN BRAINARD-BARNES: Disappeared July 9, 2007

"I believe my sister needs a voice...needs her pride back...needs the respect she had before this all happened," says Melissa Cann. She wants people to know that her sister, Maureen Brainard-Barnes, may have worked as an escort, but she was much more than that.

"She was a human being...she was a mother...she was a loved sister...she was everything to us," Cann said. "If you came up and asked her for her last penny in her pocket, she would give it to you..."

In July 2007, Maureen left her home in Norwich, Conn., and boarded a train to New York City. She went to set up appointments with men on Craigslist. At the time, Maureen was a desperate, single mother of two.

"She was getting evicted from her house. ...She needed to get some money. It was her last resort...

"These are all the jobs she called and applied for... call center, data entry...and the list goes on and on," Cann said, showing off a list. "She didn't turn to Craigslist [because] she wanted to... she turned to Craigslist because she felt like there was no way out. No one would give her a job."

Maureen checked into a Super 8 Hotel in Manhattan, and like the other young women, the 25-year-old seemed to vanish in the night.

"When I finally told myself Maureen was actually missing, that she wasn't coming back, I couldn't breathe. It was hard to breathe," says Cann.

Fearing the worst, Maureen's family went to the Norwich Police Department, submitted her name to the missing persons database, and told police she was an online escort.

"We said that Maureen went to New York and she never came back. The cop basically told us, 'Maybe your sister just ran away. Maybe she doesn't care about her kids...'" Cann said, her eyes welling with tears.

Melissa Cann says no one at the local police department took her fears seriously and the family went to look for Maureen themselves.

"My husband and my brother got on their motorcycles and actually took Maureen's picture with them and drove down to Manhattan... walked around the whole area asking people if they'd ever seen her," she said. "No one saw her, no one knew her... My brother came back and was like, 'It's a different world out there. No one wants to know you. No one cares."

On Dec. 13, 2010, Maureen's body was found alongside the others. She was the first woman to disappear back in 2007. Melissa Cann simply wishes police had worked harder to find Maureen.

"I feel like they failed me and they failed my sister. They failed these other women that were found with my sister...I feel like if the right things were done maybe these girls would still be alive to this day," she said. "We could've saved those other girls."

In March 2011, three months after finding the bodies of Melissa, Amber, Megan and Maureen, police start finding more bodies and more body parts along a once pristine beach playground; Six new sets of human remains in all.

Police believe the victims were linked to the sex trade, but only one has even been identified:

Victim No. 5: Jessica Taylor, an escort missing since 2003; dismembered

Victim No. 6: Jane Doe; dismembered.

Victim No. 7: Baby girl; possibly Jane Doe's

Victim No. 8: Asian man dressed in women's clothes

Victims 9 and 10: A female skull and a bag of female bones

Ten bodies were found in the scrub brush on Long Island and none of them belongs to Shannon Gilbert. So where is she?

Photos: Crime scene and victims

"Do you think the clue to the serial killer is in Shannan Gilbert's disappearance or is it just a coincidence?" Erin Moriarty asked Suffolk County Police Commissioner Richard Dormer.

"We don't know. She doesn't fit the pattern," he replied. "But it's still part of the investigation and we're certainly open to every possibility."

The search for Shannan began in the last place she was seen: the gated community of Oak beach, just three miles from the dumping ground.

The police started looking at three men: the man who hired her, the man who drove her, and a doctor who put himself in the middle of the investigation.

Their stories are bizarre and confusing, starting with Joseph Brewer's - the john.

Although Brewer refused to go on camera, he did meet with "48 Hours." He admitted soliciting Shannan online, but he said not for sex.

"Do you find that credible?" Moriarty asked Robin Sax, the Gilbert family's attorney. "That Joseph Brewer says that he just wanted companionship and...that he never intended to pay her? He just had her come over to his house?"

"You don't need someone to come [at] 1:00 in the morning to your home...and not expect to have some sort of sex act, and not to pay at the end," Sax said. "It's ludicrous."

Especially since Shannan was booked for two hours but stayed an hour longer.

"So presumably she was trying to make more money. She was trying to make more out of her time on Long Island," said Sax.

But Brewer himself admits he refused to pay what she asked for and they got into an argument. And shortly afterwards, she made that panicked call to 911 from inside his house.

Sax is convinced Shannan felt threatened. "The fact is she called 911. She said, 'They're going to kill me.' She was scared for her life...and she's never been seen since."

Brewer insists he never harmed Shannan. He just wanted her to leave. In fact, he brought her driver in to get her out of there. He says the last time he saw her, she was running out of his house towards his neighbor's.

That neighbor, Gus Colletti is the one who tried to help Shannan and noticed that black SUV following her.

"I could see a car coming down the road very slowly [and] would stop and then go a little bit. Stop, go a little bit," said Colletti.

It turns out she seemed to be running from the man who was supposed to be protecting her, the second man police wanted to talk to: her driver, Michael Pak.

"I ran up to his car and I said to him, 'Where do you think you're going?'" said Colletti.

Pak told Colletti he was looking for Shannan.

'I said, 'Well, I called the police... they are on their way to bring her back," Colletti said. "He said, 'You shouldn't have done that.' I said, 'Well, I did.'"

Pak, who also wouldn't go on camera, told "48 Hours" he drove around looking for Shannan for about an hour. He couldn't find her, he says. So he left.

"If you are the driver and you are responsible for this girl's transportation back home, you would think you'd give it a little more than an hour. At least to wait until the police came to force them to start looking together to be able to find her," says Sax.

Michael Pak is another odd character in this strange story. He's a dog owner - obsessed with his pet Chihuahuas, dressing them up in YouTube videos.

But Michael Pak is also a convicted felon, having served time in federal prison for conspiracy to misuse a passport.

"Michael Pak has his own checkered history," Sax explained. "He was arrested...for bringing in a Chinese lady to the United States."

Pak told "48 Hours" he had nothing to do with Shannan's disappearance and claimed he passed a polygraph "with flying colors." Police wouldn't confirm or deny that.

And then there's the third man, a total wildcard: A neighbor and retired emergency services doctor named Peter Hackett.

"Dr. Hackett is a curious character," Sax said. "He's someone whose involvement, while we can't necessarily understand, is bizarre enough that makes you wonder, what is his connection to the case?"

Just days after Shannan went missing, her sister, Sherre, says their mother got a strange call from a man they had never heard of - Dr. Hackett - who, she says, claimed he found Shannan roaming around Oak Beach the night she disappeared and brought her into his home.

"So he called my mom and he said that he saw Shannan, he held her at his house and following morning, the driver came back to pick her up and that was it," said Sherre Gilbert.

But when the sisters made their trip to Oak Beach to find out more, Dr. Hackett denied that he ever met Shannan.

"And at that point, we were just really upset," Sherre said. "We didn't know what to believe."

In press reports, Hackett denied making any call.

"Do you believe that he called her mom? Moriarty asked Commissioner Dormer.

"Yeah. Our information is that he did," he replies.

And in fact, in a letter to "48 Hours" dated June 28 2011, Dr. Hackett admits he made not one phone call - but two - to Shannan's family.

Hackett wrote: "These calls were over a year ago now and exact content is difficult to remember, but, at no time...did I suggest I had ever met her or render medical care of any sort to her."

Read Dr. Hackett's letters to "48 Hours"

Hackett says he got the telephone numbers from Shannan's friend, who was searching for her in Oak Beach, and says he called just to see if he could help in any way.

The police tell "48 Hours" that Hackett and the other two men cooperated fully and are not suspects. They also said they are not closing any doors and the investigation remains wide open.

"This case has turned into a case that's tangled with lies where I still believe there are many secrets that are yet to be uncovered at Oak Beach," said Sax.

"This is a difficult case," according to retired NYPD Commander Vernon Geberth. "This is not a 'CSI,' 'Criminal Minds' drama. This is the real deal."

Geberth, an authority on serial murder, says the stakes couldn't be higher: Catch the serial killer before he catches another victim and kills again.

Asked what stops a serial killer, Geberth told Erin Moriarty, "Incarceration or death."

Despite a massive joint effort with the FBI and state police, the killer continues to elude authorities.

"An arrest is not imminent but we're making progress," said Dormer.

In most of these cases, police sat on missing persons reports -- losing not only time, but valuable evidence. In Shannan Gilbert's disappearance, security video at the Oak Beach gate that could have provided important clues was apparently recorded over. Shannan's jacket, which Joe Brewer says sat in his driveway for days, may have been lost.

"This is a tough question Commissioner, but, if that had been a wife of a resident there who had made this panicked 911 call and then suddenly disappears, wouldn't there have been much more of a search than there was for Shannan Gilbert?" Moriarty asked.

"No, I disagree with you - strongly," Dormer replies. "Number one, when the officer responded, he didn't know that that was a sex worker. ...he conducted a search in that area. ... this was a normal - if there is such a thing - normal missing case of an adult. And the officer responded."

"This wasn't normal," Moriarty says. "She was hysterical. She said, 'they're trying to kill me' on the phone. This wasn't a normal missing case."

"I don't want to, in any way, say that we didn't do the right thing that morning," Dormer responded. "The officer - we looked at his actions and he searched that area that morning, which was appropriate..."

And, says Dormer, they have devoted unprecedented manpower and resources to finding Shannan.

"We kept going back there over the months...and never gave up," he said.

It paid off. On Dec. 6, 2011, a year-and-a-half after Shannan disappeared, they got their first big break.

"They found a pair of jeans, a pair of shoes, cellphone, a pocketbook with ID in the pocketbook belonging to Shannan Gilbert," Dormer told reporters at a press conference.

Video: More of Moriarty's interview with Dormer

But still no Shannan. Investigators drained the wetlands. Then, on Dec. 13, the discovery so many had been hoping for... and yet dreading.

"We have this day, at approximately 9:14 a.m., located a set of skeletal remains," Dormer told reporters. "We believe at this time to belong to the missing Shannan Gilbert."

Shannan had never left Oak Beach after all:

2:00 a.m.: Shannan arrives at client Joe Brewer's house.

4:51 a.m.: Shannan makes that panicked call to 911

5:15 a.m.: Still on the call, she runs five houses down to neighbor Gus Colletti's door begging for help.

Around 5:30 a.m.: Shannan is spotted at Dr. Hackett's house. This is the area where her belongings were found. But her remains - were a quarter mile away-- and only 100 yards off of Ocean Parkway.

Asked if he believed Shannan Gilbert was murdered, Dormer told Moriarty," There's no evidence whatsoever to show that anyone was out to harm her that night..."

"She clearly was in fear for her life," noted Moriarty.

"Now, we're awaiting results of the medical examiner's examination of her remains. And so we have to have an open mind on that," Dormer said. "But I would caution right now that we don't believe that she was a victim of foul play..."

Even though the autopsy is not yet complete, the police commissioner says he believes a disoriented Shannan ran into the tangled brush of the marsh -- possibly trying to make it to the parkway -- and accidentally drowned.

"But does it make sense, Commissioner, that her belongings would be found in one spot, including her clothes and her body a quarter mile away?" Moriarty asked.

"That's explainable because she's hysterical," Dormer replied. "And she's discarding her possessions as she moves along."

"But her clothes?"

"Well, her jeans could have come off from running in that environment," Dormer explainer, "and that is a possibility that the jeans came off and she kept running..."

Vernon Geberth isn't buying it.

"Did she take her clothes off before she went for a dip," Geberth asked. "I think that the fact that her purse, her cell phone, and her pants were found in this location and her body someplace else is highly consistent with someone dumping the body and getting rid of evidence."

CBS News has learned that the medical examiner will be going "bone by bone" looking or any sign of a violent death. If the answer is yes... who killed Shannan Gilbert?

"Is there any chance that Shannan Gilbert is the 11th victim of this serial killer?" Moriarty asked Dormer.

"There's no indication whatsoever that she's connected to the 10 other victims that we found," he replied.

"All I can say is that Shannon Gilbert fits the same profile and victimology as the other girls who were found," Geberth said. "So I find it highly unusual that they would be talking about her as an accidental death."

In an eerie coincidence, the remains believed to be Shannan Gilbert were found almost one year to the day that police discovered the first victims of the serial killer. Many of their families just happened to be in Oak Beach for the anniversary.

Melissa Cann lost her sister, Maureen.

"I'm still numb over everything that's been on today -- going to the girls' sites, putting their crosses on and then coming to find out they found Shannan. It hurts," Cann said. "It's like we are a family. And it's like losing my own sister all over again."

Shannan Gilbert who dreamed of becoming a singer, sparked the largest homicide investigation in Long Island history... and for a brief moment we all took notice.

Said Cann at a memorial held on Dec. 13, "We're going to have a moment of silence to remember ... Shannan for the loving daughter, the loving sister... Remember Shannan for Shannan."

On Saturday, Dec. 17, the remains found at Oak Beach on Dec. 13, were positively identified as Shannan Gilbert. She was 23.

Police ID remains as missing N.J. woman

Suffolk County Crime Stoppers is offering a cash reward of up to $25,000 for information leading to an arrest in the Long Island Serial Killer case.

Anyone with information is urged to call -800-220-TIPS (8477). Tips can also be submitted online.