AP - Albuquerque Police provided this undated photo of Tyruss 'Ty' Toribio, Police said Thursday, May 21, …

ALBUQUERQUE, N.M. - A mother playing with her children at a park spotted a little black sneaker sticking out of the sand underneath the playground equipment. Figuring a youngster had lost his shoe, she bent down to pick it up. It was strangely heavy.

She had made a ghastly discovery: a dead little boy, buried in the sand.

For nearly a week, who the toddler was, how he died, and who put him there were a chilling mystery until Thursday, when a drawing of the youngster circulated by police led to the arrest of a young mother on murder charges.

Albuquerque police said Tiffany Toribio, 23, confessed to suffocating her 3-year-old son, Tyruss "Ty" Toribio, as he slept on the climbing gym - a crime so cold-blooded that neighbors struggled to comprehend it, and even veteran officers became choked up.

"For a mother to kill her own child is unfathomable. Most people can't even imagine how you could even think about doing something like that," said Cmdr. Michael Geier. "We'll never really understand why that happened, but we now understand the dynamics of what led up to that."

Toribio was homeless and sleeping in the park, having been kicked out of her mother's home and a friend's apartment in the days before her son's death because she was ignoring the boy and withholding affection, investigators said.

"What makes this story especially sad was when asked the reason why she took Ty's life, Tiffany said that she did not want him to grow up with no one caring about him the same way that she had grown up with no one caring about her," said Police Chief Ray Schultz, his eyes watery and his voice thick with emotion.

What had baffled police after the discovery of the body was that the chubby-cheeked boy appeared to have been well-fed, showed no signs of physical abuse and was wearing a matching outfit that seemed to suggest he had been well-cared for.

But when no came forward to report a missing child, police came to suspect that whoever buried Ty was a parent or someone taking care of him.

Police went door-to-door in the neighborhood around the park. They contacted schools, daycare centers and homeless shelters. They asked families at other playgrounds about the boy. They reviewed hours of video surveillance tapes from courthouses, hospitals and stores. They followed up on more than 100 tips.

The break in the case came just hours after police released a photograph-like picture of the boy. Family members and others called a tip line to say the picture of "Baby Angel" - as neighbors living near the park nicknamed him - looked like Ty.

Then, police received a tip that Toribio was on her way to the police station to turn herself in. Officers stopped her as she was walking on the street.

The police chief said Toribio told detectives that she suffocated her son in Alvarado Park before dawn on May 13 by putting her hand over his mouth and nose. She said she had second thoughts and performed CPR on the boy, resuscitating him, but reconsidered and smothered him again. Investigators said she then buried him under the climbing gym's hanging bridge, where the body was found two days later.

Schultz called it "somber day" in Albuquerque.

"He was a very special child and that's what makes this case so hard for everybody within the Albuquerque Police Department that's worked on it for the last six days," he said.

Schultz said Toribio attempted suicide in jail and was under close observation. A single mother, Toribio had no criminal record or history of drug or alcohol abuse, the police chief said.

Julie Gonzalez, who lives near the park, described Ty as "such a good little boy, so quiet, mild." But Gonzalez said that the boy's mother was "always partying" and that police would have to be called when fights broke out among the partygoers.

Toribio did not have an attorney Thursday morning, and attempts to locate family members were unsuccessful.

Toribio is a member of the Zia Pueblo Indian tribe. Tribal Gov. Ivan Pino said the tribe has asked that Ty's body be returned to the pueblo for burial. People living near the park raised about $4,000 for a funeral for the boy.

"Let the Pueblo of Zia go through its healing process right now," Pino said. "Give us the respect to go through our mourning at this point."

Neighbors gathered at a makeshift memorial at the playground consisting of candles, flowers, stuffed animals and toy trucks. Children played on the equipment; parents and grandparents wept.

"We named him `Baby Angel' and it's important now that we know his real name," said Sarah Sandoval. "Now, his mother will find out this baby has a lot of people who love him and will do anything for a child."

Stephanie Rael, a mother, said she wished she had been at the park when Ty died.

"I could have helped her. I could have called someone. We could have saved him," she said. "We're here in a public place. She could have left him here alive and any one of us could have saw him and taken him or gotten her help."