ST. PETERSBURG — Cynthia Calleia knew that her 9-year-old daughter had serious problems.
She admitted trying to suffocate one brother. And she heard voices telling her to kill her mommy.
Still, investigators say Calleia left her youngest son, 4-month-old Antoine Powell Jr., alone with the girl.
In March, the 9-year-old dropped her brother on the floor and heard a loud crack. Another sister dragged him by the arm "like a doll." He wound up with a broken arm, leg and five fractured ribs. His mother waited to take him to the hospital, and he died on April 15.
On Tuesday, authorities arrested Calleia, 30, on a charge of aggravated manslaughter of a child. They said she neglected the baby by leaving him with the 9-year-old and failing to take him to the hospital earlier.
Investigators said Calleia often left the boy in the care of his siblings while she stepped out, sometimes to chain-smoke cigarettes.
Neighbors at the Park View Apartments, a cluster of units on the 600 block of 22nd Avenue S where police say the abuses occurred, confirmed what the court records show: Calleia was often absent, and her daughter was in charge of the kids.
The 9-year-old "was always just alone, always by herself," said neighbor Stephaney Carter, 37. "She would take the bus by herself."
Investigators believe the girl, whose name was withheld, injured the baby some time in March. Court records state she dropped her brother because he wouldn't stop crying.
Calleia denied knowing that her son was hurt in the March incident. When she took the baby to All Children's Hospital on March 17, she said she didn't know of any injury before that day. She said she noticed his arm was limp that morning, about eight hours earlier, and thought one of her other children had pulled his arm out of the socket.
But two babysitters told investigators that they explained to Calleia that the infant needed to see a doctor. The boy wailed through the nights.
"There is absolutely no way that Cynthia Calleia could have held or picked up this victim, listened to him scream, and not have known there was something wrong with him," investigators reported the babysitter told them.
An autopsy determined that he died from complications from blunt force trauma. A doctor said one fracture appeared to be a week or more old.
Calleia, who has no criminal record in Florida, told police that she knew her daughter had mental health problems. Court records state that Calleia chose not to give her daughter medication for attention deficit hyperactivity disorder.
Calleia used the Baker Act in 2003 to temporarily institutionalize the girl after she caught her shaking her other baby brother back and forth. When she asked her daughter what she was doing, the girl answered "I'm killing my brother."
Investigators say it's implausible that Calleia didn't know about the boy's injuries after the March incident, as she said. Tuesday morning, Calleia was arrested at her room at the Dennis Hotel building, 326 First Ave. N. She faces up to 30 years in prison if convicted on the first-degree felony.
The girl, and her two siblings — a toddler and a 5-year-old — were placed in the care of the Department of Children and Families.
Aggression in young children is common but deadly violence is rare, said Dr. Stephen Mandelbaum, director of the outpatient child psychiatry clinic at Cedar-Sinai Medical Center in Los Angeles. He added that it's very difficult for mental health care professionals to predict violent behavior.
"These are really complex problems that require very complicated, integrated solutions from multiple agencies," said Mandelbaum, who would not comment on this case in particular.
The legal system often struggles with how to deal with very young children accused of killing babies.
In 2005, the Hillsborough County State Attorney's Office charged an 8-year-old boy with aggravated manslaughter in the beating death of his infant half-sister. But a judge decided the boy was incompetent to stand trial because of his young age.
In 1983, two sons of a babysitter, ages 7 and 9, were arrested on charges that they killed an 8-month-old girl in St. Petersburg. The younger boy testified against his older brother. His first-degree murder conviction was thrown out by the Supreme Court, but facing a retrial he pleaded guilty and was sentenced to remain in a state youth facility until he was 19.
Outside their old apartment, Carter, the neighbor, said she wasn't surprised Calleia's absence resulted in tragedy.
"If my kids were doing that," she said, "I'd blame myself."
Times researcher Caryn Baird contributed to this report. Stephanie Garry can be reached at (727) 892-2374.