Arrest Imminent in Kyron Horman Search?

After getting thousands of tips, the investigation into missing 7-year-old Kyron Hormon appears to have gone full circle, and now an arrest could be right around the corner.

CBS News correspondent Priya David Clemens reported Monday from Portland, Ore., that police have fielded more than 3,300 tips from around the world. However, on Saturday, they came back to Kyron's grade school -- the last place he was seen. Clemens reported many believe the last person who saw him, his stepmother Terri Horman, could hold the key to bringing him home.

Investigators returned to Skyline Elementary School over the weekend, searching for clues that might lead them to Kyron Horman.

Officials say they've made significant progress in the criminal investigation, but are not releasing any details. In a written response to journalists' questions, they say Kyron's stepmother "has been cooperative...and other times she has not." Since hiring a defense attorney on June 28, she's been silent.

C.W. Jensen, a retired police captain, told CBS News, "If the investigative team found out what happened to Kyron, Terri Horman would be arrested imminently."

Kyron's parents have begged Terri to talk, Clemens reported. They are also pleading with her close friend, DeDe Spicher, to cooperate. They claim Spicher is giving Terri advice that is not in the best interest of their son. Last week, the FBI searched her home.

New questions are still emerging about Terri Horman's actions the day her stepson disappeared. Several hours remain unexplained. Terri Horman claimed she left Kyron at school at 8:45 a.m. and at 11:39 a.m. she went to the gym. In that three-hour gap, she said she went shopping and drove her 19-month-old daughter around to soothe an earache. But that has not been corroborated by anyone.

Jensen told CBS News, "All these things add up to a human being that doesn't make sense."

Terri Horman posted Kyron's picture on her Facebook page that afternoon. Later, both Terri and Kyron's father Kaine went to meet the school bus. Kyron was reported missing seven hours after he vanished. In a recent interview, Kyron's biological parents said Terri's behavior that day raised their suspicions.

Desiree Young, Kyron's mother, told Clemens, "I can tell you what I ate that day, she can't tell you where she was.

On "The Early Show" Monday, Bruce McCain, former captain of the Multnomah County Sheriff's office, who just retired last year, appeared on the broadcast to offer his insights into the handling of the case.

"Early Show" co-anchor Erica Hill asked McCain about new reports that Terri Horman told her stepson's teachers that he had a doctor's appointment later that day.

Terri Horman reportedly said she alerted them to the appointment that would happen that following Friday.

McCain said this report is "quite significant" because the day Kyron disappeared was the last day of school.

He explained, "A doctor's appointment the following Friday would have been pretty irrelevant to the school but the critical thing about this June 4th doctor's appointment is that that put the school in a position of not being concerned at all, that Kyron was not in his class, wasn't at lunch or the bus that afternoon. So, it looks like at least at this point Terri was able to bring Kyron to school, establish his presence there, and then perhaps take him away, at least that's the theory they're working on, without the school picking up the phone and call Kaine (Kyron's father) at work, for example."

Terri Horman is currently not a suspect in the case.

But McCain said there seems to be some sort of premeditated plan at work here.

"Especially with the deceptive answers she gave later about, 'Gee, I think I meant June 11th,' which is long after school is out. The key is going back, refocusing and reconstructing every hour and minute she spent on that fateful June 4th to find out exactly where the holes are in her original story."

Hill pointed out in the Terri Horman's timeline of that morning there is a three-hour period where we're not really sure what was happening between the time she dropped Kyron off, the last time she saw him at school, and showed up at the gym. Terri Horman's friend DeDe Spicher is also being questioned about those times.

McCain said those periods are significant, he said, "especially given the close relationship between DeDe and Terri."

McCain said, "The investigators seem to be putting pressure on Terri's closest friends, associates and family to basically tell them, it's time to get on the right side of this issue. DeDe right now seems to be on Terri's side and we'll see how long that lasts. That critical 90-minutes for both of them is where they seem to be focusing efforts on June 4th day."

Hill added Kyron's father and mother say Spicher is hampering investigation. The sheriff's department recently came out and answer questions from journalists via e-mail, Hill said. One question that was asked was whether they have any information to believe whether Kyron is alive. They didn't answer it directly.

McCain said, "They could not bring themselves to say yes. The best they could do is, 'We continue to hope.' That put the sheriff's office in the same position as thousands of others looking for Kyron."

He added, "Bottom line is Kyron is either alive and dead, and that's the blunt truth right now. So, right now the key is to try to put pressure on Terri and perhaps through an arrest on an unrelated criminal episode. This would be the murder hire for-hire plot. Using that could potentially leverage the truth out of both people involved in this. Right now, Kyron is simply missing and nobody, including investigators, seem to know what happened to him."

Clemens added the Multonomah County sheriff is expected to speak on Tuesday after several weeks of silence, which has many here hoping for answers or a break in the case.