It's a horrifying crime that has so many people outraged.

A 13-day-old baby girl is dead. Sheriff Bob Gualtieri says she was brutally pummeled and killed by her 6-year-old brother and now the 62-year-old mother is facing charges.

Kathleen Marie Steele of North Redington Beach has been charged with aggravated manslaughter and neglect for the infant's death.

On Monday, Steele left the baby, also named Kathleen, in a vehicle with her two siblings while she went into a cell phone repair store. While she was inside the store the infant started crying and that's when the 6-year-old boy snapped, Gualtieri said.

The 6-year-old brother picked up the baby and dropped her on the floor of the vehicle, then "slammed" her around the vehicle, the sheriff said.

The boy later admitted to investigators what he had done, said Gualtieri.

The sheriff says at just 13-days-old, the little girl was killed at the hands of her brother. The boy told investigators how he did it.

“I took the baby, and I slammed her like this, and slammed her down, and pushed her up into the ceiling. What he was talking about when he pushed her up into the ceiling, he was holding her up, then he said he was flipping her this way and flipping her that way and she would fall. The way he was describing it is he was tossing that baby around like a ragdoll,” says Sheriff Gualtieri.

Gualtieri said the baby's skull was cracked and probably died in the vehicle.

Steele left the children in the vehicle by themselves for more than a half hour, he said. After leaving the store, Steele drove to Enterprise Rent-A-Car and spent another half hour there before returning home, the sheriff said.

The sheriff says the mother is to blame. The boy told her about the baby's condition, yet she ran another errand, before returning home. She called a neighbor, who is a nurse, to help. The neighbor recognized the infant was dead, but called 911. The child was taken to St. Petersburg General Hospital, where she was officially declared dead.

Because of the child's age, the boy will not face criminal charges, Gualtieri said. Due to our crime guidelines, 10News will not identify the boy.

“The mistake is with Kathleen Steele, not a 6-year-old boy,” Sheriff Gualtieri says.

Back in 2010, Kathleen Steele appeared in a reality show “55 and Pregnant." The financial advisor and her husband had been awaiting their first son.

Since then, Steele's husband died of cancer in September 2011. The sheriff says with her husband’s frozen sperm she had another son, who is now 3 years old, and just gave birth to baby Kathleen the end of July.

“Yeah, I wouldn't do it,” says neighbor Marie Molina.

The family's North Redington Beach neighbors say the 6-year-old brother apparently didn't like the idea of a new baby.

An accidental fire started in their home days before her arrival.

Steele was under investigation by the Pinellas County Sheriff’s Office Child Protection Investigation Division at the time. At just 3-days-old, the baby fell from her car carrier down the stairs of a Treasure Island hotel. Despite a brain bleed, investigators ruled it an accident.

Days later, the sheriff says a complaint to the DCF hotline about the mother's inadequate supervision couldn't be proven. Florida Department of Children and Families Secretary Mike Carroll said his department had no prior involvement with the family.

“I'm 100 percent confident there's nothing else we could've done or should've done. We couldn't have prevented this from happening,” say Sheriff Gualtieri.

The school district says the first grader will not be returning to Lakewood Elementary. There will be counselors for staff and students on Friday. Pinellas County Schools says it will continue to work with the Sheriff's Office and Child Protective Services as they establish the best plan moving forward for the child.

Superintendent Dr. Michael Grego says, "This is a heartbreaking situation. The death of a child, of an infant, is so hard to process. I am deeply saddened by this. In the school system our role as educators is to support our students as best we can, even when faced with the unthinkable.”

The boys are now separated and in DCF foster care.