DURHAM, N.C. -- Amy Pittman learned on her first day in jail to bottle up her grief.

As soon as she arrived, guards took her shoelaces so she wouldn't try to hang herself. Cry too much or scream too loud and she feared they would come back to take everything she had left - her clothes, a sheet, a plastic spork.

But how could she not? How could anyone? Ten weeks before, Pittman was a single mom who worked overnight shifts as a gas station cashier to keep her three kids fed and clothed.

Now, alone in a cinderblock cell, she faced criminal charges for not doing enough to protect them. She pictured her youngest, Christian, 9, in his coffin. Blue shirt neatly tucked. Cold to the touch. Dead at the hands of his 12-year-old brother, who had accidentally shot him in the back.

"Five minutes can change your whole life," said Pittman, 38. "I wish every day that I would have stayed home."

Children under age 12 die from gun accidents in the United States about once a week, on average. Almost every death begins with the same basic circumstances: an unsecured and loaded gun, a guardian's lapse in attention. And each ends with the same basic questions: Who is to blame, and should the person be punished?

An investigation by the USA TODAY Network and The Associated Press found those questions are answered haphazardly across the nation.

Nearly identical accidents can have markedly different outcomes. A shooting that leads to a prison sentence in one state can end with no prosecution at all in another.

In 2015, a baby sitter in North Carolina was charged with involuntary manslaughter when a 2-year-old she was watching shot herself with a 20-gauge shotgun she found on a table. Two months later, police and prosecutors in Colorado opted not to charge a baby sitter after a 9-year-old boy was shot by his brother. The sitter had briefly left the boys unattended, and they found his loaded .38 Special in his pickup.

Grandparents in Detroit, both 65, faced manslaughter and weapons charges that could have sent them to prison for 17 years after their 5-year-old granddaughter found a loaded pistol under their pillow and shot herself in the neck. In Illinois, a grandmother pleaded guilty to a minor gun charge and received probation after a 6-year-old boy found a revolver in a bedroom closet and shot himself: "Oh my God, I killed my baby!" she screamed to police at the scene.

In the days after the April 2014 death of Amy Pittman's son, a second-grader with thick black hair he often wore in a mohawk, the decision of whom to blame fell to Cindy Kenney, an assistant district attorney in Durham whose usual mix of cases includes murders and sex assaults against children. She said Christian's death seemed to be no ordinary accident.

Investigators said that in addition to the shotgun that killed Christian, they found a handgun under a mattress in a bedroom and an assault rifle in the closet. They found 100 rounds of ammunition in a grocery bag, and Kenney would later tell a judge that Pittman's underwear drawer "had more ammunition in it than it did panties."

In a country with almost as many guns as there are people, it's not unusual to find loaded weapons within children's reach. One study published in 2008 in the journal Health Education Research found that firearms are present in about one-third of all homes with children nationwide. Guns in half of those homes were kept unlocked; guns in one-sixth of them were kept loaded.

In that sense, the accident that killed Pittman's son was like many others. What set it apart, prosecutors said later, was that she should have known better.

Kenney said someone had called the county's child welfare agency to say Pittman's children were seen chasing one another through the neighborhood with guns. A social services worker met with her, warned her that it was illegal to leave guns near unsupervised children and offered to buy her a gun safe so she could secure them. Pittman's response, Kenney said later, was that the county should stay out of her business.

Pittman tells a starkly different story. She said she was never contacted by social services officials and insists she was unaware of the guns in her house, which belonged to her boyfriend. (Kenney said prosecutors did not charge her boyfriend because, unlike Pittman, he did not have a legal duty to keep her kids safe.) Police, prosecutors and the social services office declined to release any records about her son's death.

Prosecutors throughout the country say deciding whether to bring charges is seldom easy. Parents are suffering, and heaping a criminal prosecution on top of that grief may not do much to teach others to handle their guns more carefully. In some cases, the decision to seek charges can cost the surviving kids their parent.

Kenney did not struggle with her decision.

"Accidents happen, but this case mandated our charges," Kenney said. "It's awful, you don't bring these charges lightly, but all of this could have been prevented."

Less than three months after the shooting, a grand jury indicted Amy Pittman on charges of involuntary manslaughter and three counts of felony child abuse. Pittman, the grand jury said, "willfully and feloniously did kill and slay Christian Pittman."

Pittman dropped her children with their grandmother and waited at a friend's house to be arrested. She wouldn't see them for almost a year and a half.

Putting parents in jail

Journalists from the USA TODAY Network and the AP spent months using information from the nonpartisan Gun Violence Archive, news reports and police records to examine all of the 152 accidents from 2014 to 2016 in which children under age 12 either killed themselves or were mistakenly shot and killed by another child.

The review found that about half of those deaths led to a criminal charge, usually against adults who police and prosecutors say should have watched the children more closely or secured their guns more carefully. The rest of the time, officials decided the grown-ups had broken no laws, or perhaps had simply suffered enough. In many cases, there was little to distinguish those deaths that led to a criminal charge from those that did not.

Felons were the only exception. Because it is illegal for anyone who has been convicted of a felony to possess a gun, almost every felon involved in an accidental gun death faced criminal charges.

Even when gun accidents do lead to criminal charges, most parents and guardians still avoid prison. Pittman was one of 50 people to be convicted of a crime following the accidents the news organizations reviewed, although a few cases are pending. Slightly less than half of those people were sentenced to probation; the rest were ordered locked up, typically for about four years.

For parents and guardians who are not felons, the stark division in outcomes reflects the struggle prosecutors face after almost any accidental death.

"You feel an enormous amount of sympathy for these parents because it's the most unimaginable loss there is when you lose a child. Prosecutors understandably struggle with the deterrent value with filing charges," said Jennifer Collins, dean of Southern Methodist University Law School, who has studied prosecutions of negligent parents.

The same pattern plays out when children drown in swimming pools or suffocate in hot cars. Collins studied such cases a decade ago and found that about half ended in prosecutions; much of the time, prosecutors applied what she called a "suffering discount" as they looked for a balance between deterrence, retribution and mercy.

The government's most recent official count of gun deaths, by the U.S. Centers for Disease Control and Prevention, identified 77 minors who died in gun accidents in 2015, but the AP and USA TODAY counted 146 for that year, including 96 in which a child either shot themselves or another child

By either measure, gun accidents account for a small share of children's deaths in the U.S. About the same number of children die each year in hot cars and poisoning incidents. About five times as many die in fires and 12 times as many drown.

Gun accidents pose a particular challenge for police and prosecutors who must decide whom, if anyone, to hold responsible. One of the reasons why it's so difficult is that it's not always clear what criminal charges would accomplish. Prosecutors worry punishment won't do much to change how other parents keep their guns. And compared with losing a child, the threat of spending a year or two in jail can seem almost inconsequential.

Casey Mercer sometimes thought about jail in the weeks after his 3-year-old daughter, Alexis, shot herself with a gun he had left on the sofa. But he didn't fear the idea of being locked up.

"It's hard to explain. It was already as bad as it was going to get," he said.

Mercer kept eight firearms at his home in Lake Charles, Louisiana, midway between Houston and New Orleans. He cleaned them one morning in 2015 before leaving for work, but forgot one, a semi-automatic Glock pistol, on a couch. He texted his girlfriend, Angel Savoy, to put them away before she got home with Alexis.

In the time it took Savoy to put the family dog outside, the toddler fired the Glock through her eyelid. Alexis died at the hospital a short time later.

"It was the most painful thing you can possibly go through," Mercer said. "I worked with the police; whenever they needed something, I was there. I was worried (about jail), but it wouldn't have made it different for me."

The sheriff's investigation eventually made its way to Cynthia Killingsworth, first district attorney for Calcasieu Parish. Largely because of the text message, Killingsworth decided against any charges for Mercer or his girlfriend.

"What else can I do to those people to have this not happen again?" Killingsworth said. "We're here to protect society. That's our job. There's nothing I could do from a criminal standpoint to make anything change."

Prosecutors elsewhere have taken a different tack. In Detroit, after a series of high-profile shootings, prosecutors have aggressively sought to charge parents and guardians after gun accidents. The mere presence of an unsecured gun near children is sometimes enough for them to bring criminal charges and the threat of years in prison, assistant county prosecutor Maria Miller said.

"I shot my brother"

The night Amy Pittman's son died, she gave her kids chicken nuggets for dinner and told them to take baths before bed. She left her 14-year-old daughter in charge and went out to pick up one of her friends. She said she'd be back within an hour.

Pittman, with brown hair and arms covered with cartoon tattoos, speaks with a raspy, Carolina drawl. She grew up in Durham and left high school at 17 when she became pregnant with her first son. Three different fathers never played a role in parenting her four kids. USA TODAY and the AP are not publishing the names of her surviving children.

She worked as a gas station cashier, sometimes overnight to afford the rent on a tiny house on a gravel road that backs up to an industrial warehouse. She saved enough to give her kids shoes and video games on their birthdays. She had racked up speeding and traffic tickets but had been charged with a crime only once, a misdemeanor for selling alcohol to a minor at her job at the convenience store.

Many days, Pittman finished work at 3 a.m., then stayed awake long enough to help Christian with his homework before school. She made it to the other kids' basketball games and cross-country meets, but sometimes depended on her father or her boyfriend to make sure they got dinner when she was at work.

While she was gone that evening, Christian's older brother found the shotgun leaning against the refrigerator. He picked it up, shook it and decided it was unloaded. He later told the police he wanted to play with Christian, so he pointed the gun at the 9-year-old and pulled the trigger.

The gun fired. Christian fell. His brother ran into the night, screaming for help.

"I shot my brother," he shouted, according to court records. "He's on the floor. Call. We need help."

Christian was dead when detectives arrived.

Pittman arrived home to find police officers crowded inside near Christian's body. His sister was in a squad car and his brother was at the hospital.

That night, after police questioned her, Pittman made her way to Duke University Hospital, where doctors were treating Christian's older brother, who had been hit in the face by the butt of the shotgun after it went off. She found him holding a plate of pepperoni pizza - Christian's favorite - that he was saving for his little brother.

"That was the saddest moment. I had to look at him and tell him his brother didn't make it," Pittman said.

The shooting left the brother distraught, said Scott Gray, senior pastor at Liberty Baptist Church, where the family prayed each Sunday. The older boy talked about ending his life, too.

"He fell into my arms and we prayed and cried together," Gray said about the night of the shooting.

Gray still frequently preaches out of the red, dog-eared Bible Christian received through a church youth group. He used it at the boy's funeral.

At Glenn Elementary, where the boys attended second and fifth grade, Principal Cornelius Redfearn slowly erased Christian from his classroom. The school left his things at his desk for two weeks, then moved his desk away from his classmates, then started taking away his papers, until eventually all of his things were gone.

Kids and guns

Prosecutors regularly determine that the combination of kids and unsecured guns isn't enough of a reason to lock someone up after an accidental death.

Wendy Brock wondered as much on the night her son died in 2015. Still at the hospital in the hours after doctors concluded they could not save the boy, Brock asked the police officer interviewing her an obvious question: "Are we going to jail for this?"

Brock's son, Jaxon White, had turned 3 two days earlier. His family celebrated with a party. Sunday was a beautiful day, and the boy was out in the yard of the family's home in Jefferson, Georgia, about an hour outside Atlanta, riding his four-wheeler and playing with a new bubble machine.

His parents, Brock and Roger White Jr., were washing Roger's pickup in the driveway. The boy climbed in the open driver's side door, found the handgun his father kept in the center console and stood on the seat.

His father, nearby, screamed the boy's name to tell him to put down the gun, which was pointed up as Jaxon looked down the barrel.

Then, a loud pop.

The boy collapsed from a gunshot wound to the head. His father cradled him in his arms as he screamed for Wendy to call 911. Jaxon was breathing, barely, when medics arrived. His pulse stopped in the ambulance.

A Jefferson Police Department officer later wrote that White appeared to be delusional and was seen talking to himself, saying "I knew better." Officers found other guns around the house, including a loaded gun on top of a mirror on a dresser and the loaded revolver Brock kept in her minivan.

Nevertheless, Special Agent Jeremy Burton of the Georgia Bureau of Investigation told him, "You are certainly very careful with where you place your firearms," but that they would be temporarily taken away for safety reasons, according to a recording of the conversation. Jaxon's death, Burton said, appeared to be "just an accident, a very terrible accident."

District Attorney J. Bradley Smith closed the case without filing charges, citing a lack of criminal intent.

"While looking in hindsight, additional measures could have been taken to prevent this tragedy, the lack of those measures does not rise to the level of reckless conduct or criminal negligence," he wrote in a letter to the police. "I see no purpose in punishing this family any further."

Brock and White declined to comment; their reactions were captured in police records and recorded interviews with investigators.

The boy's grandmother and Roger's mother, Sharon White, praised the decision not to file charges, saying the accident had devastated everyone in the family.

"Could you imagine in that situation, after all that, them charging him and making him go to jail for that?" she said.

Some states have laws meant to limit children's access to loaded weapons. But the "child access prevention" rules have run into opposition from gun-rights groups including the National Rifle Association. A spokeswoman for the NRA, Jennifer Baker, said the group opposes "one-size-fits-all government mandates" and believes existing laws are enough to handle gun accidents.

Both the NRA and gun-control groups have focused instead on education campaigns that encourage parents to safeguard their weapons.

"She lost everything"

Pittman pleaded guilty on a Thursday in July 2015. Only her father and her lawyer came with her.

Pittman had told everyone she didn't know about the guns; all she wished she had done differently, she said, was stay home that night.

"It weren't her fault. It weren't. It was that guy she was living with," said Pittman's father, Frankie.

But on that day, she faced a judge and said she was ready to accept the blame for Christian's death.

Do you know, Judge Paul Gessner asked, that you're pleading guilty to involuntary manslaughter and child abuse?

"Yes," she said.

"Are you in fact guilty?"

"Yes."

She sat while Kenney, the prosecutor, explained why she belonged in prison. "Egregious" lack of care, she called it.

Gessner sentenced Pittman to two years in prison. With credit for the time she'd already spent in county jail, she would be out in one. But Gessner left little doubt that the sentence signaled the end for Pittman's family. Her remaining children would go to foster care; she could not communicate with them unless a therapist approved.

"The effect of this judgment is devastating. The whole thing is devastating," the judge said.

Pittman's lawyer, Woodrena Baker-Harrell, said the tragedy of Christian's death would cost the family far more than a two-year prison sentence. "She's going to suffer for the rest of her life. Even if she got a life sentence, you can't punish her more than she is already imposing on herself," she said. "It's a mother who just lost her child."

Now released, Pittman said her goals are "go to work, save money, stay out of trouble and get my kids back."

She sees her two youngest children only once a month, for an hour, in a neutral location while a social worker keeps watch.

She visits Christian more, sitting on the lawn next to the bronze plate with a picture of a teddy bear on a swing that marks his grave. She added his name, surrounded by a pair of wings and a halo, to the collection of tattoos on her arm, a reminder of her youngest child she can carry with her.

She also carries the question: "Am I as bad of a mom as they say I am?"

Nick Penzenstadler reported for USA Today; Ryan J. Foley and Larry Fenn reported for the AP.