NORTH REDINGTON BEACH, FL (WFLA) – Neighbors of a 6-year-old boy accused of beating his 13-day-old sister to death say they are shocked and saddened by the news.

The boy’s mother, Kathleen Marie Steele, 62, was arrested and charged with aggravated manslaughter in connection with the death of her infant daughter Kathleen, who was conceived via artificial insemination.

Steele faced a judge Friday morning. Her bond was set at $100,000.

Investigators say Steele was negligent when she left her three kids, ages 6, 3, and 13 days, alone in a van while she went inside a business. The 6-year-old boy shook his little sister when she started crying, spun her, dropped her and slammed her head against the ceiling.

Steele’s neighbors were shocked after hearing what happened to the baby girl who lived in a large home on Bath Club Boulevard in North Redington Beach.

Manny Molina lives down the street from Steele and says he often heard her yelling in anger at the children. “Pretty much all weekend,” said Molina.

Still, he couldn’t believe the details of the 13-day-old baby’s death when he heard them.

“I don’t know how things like that can happen, how a 6-year-old can turn that bad that quick. I don’t know what was going through his mind,” said Molina.

Pinellas County Sheriff Bob Gualtieri said that people have told detectives that she didn’t care for the children properly.

“Frankie and Phillip, at 6 and 3, were running amok, unsupervised, and what others saw was consistent with what happened on Monday, and that she didn’t care for the kids and was negligent and neglectful and abused them by leaving these kids in the car,” the sheriff said on Thursday.

The disturbing killing has many people wondering how something so terrible could happen to the baby girl.

Steele’s home caught fire and she and her children had been staying at a motel. No one is at Steele’s home to pick up newspapers that are delivered each morning. The headline of a newspaper delivered on Friday morning was about the killing of her daughter.