The 6-year-old boy took the doll and showed detectives what he’d done.

He twisted its body and punched its face, flipped it upside down and right side up again. He slammed its head on the ceiling then dropped it to the floor.

If the doll had had eyes like his baby sister, just 13 days old on the afternoon it all happened, they would have been swollen and severely bruised. The doll’s nose would have bled, its skull would have cracked, its skin would have turned cold and blue.

That’s what was revealed in the autopsy this week of Kathleen Bridget Steele, born July 26, 2016, in St. Petersburg, Fla. She’d almost made it through her second week of life when her big brother ended it, authorities said, beating her to death inside a parked van on Aug. 8, all because she wouldn’t stop crying.

The boy, a first-grader, will be charged with no crimes, the Pinellas County Sheriff’s Office said, because, ultimately, he is a victim, too.

Instead, authorities blame his mother.

Kathleen Marie Steele, 62, was arrested late Thursday afternoon on a felony charge of aggravated manslaughter of a child. It was while she was inside a cellphone repair store for 38 minutes that her eldest child killed her youngest, authorities said. She left all three of her young children — ages 6, 3 and 13 days — unattended inside her locked rental van, the windows rolled up, the engine off.

“Those of us that have been doing this and been in this business for a very long time have never seen anything like this,” Sheriff Bob Gualtieri said in a news conference Thursday. “… Nobody can ever recall a situation in our history here in Florida where we’ve had a 6-year-old kill a 13-day-old.”

The crime was a “vicious brutalization of a baby,” he said.

Steele is being held in the Pinellas County Jail on $100,000 bond. She will appear before a judge at 1:30 p.m. Friday and based on local media reports it is unclear if Steele is represented by a lawyer as of Friday morning.

“It’s a very sad case, to say the least, but the accountability belongs with Kathleen Steele,” Gualtieri added, “the mother who is, by all accounts, ill-equipped to have a baby.”

Since the day her baby died, Steele has been “aloof,” Gualtieri said, unwilling to admit her son was at fault, initially disinterested in the baby’s condition. On the night of the beating, as emergency workers tried to revive the little girl, Steele did not help, the sheriff said, but instead walked to her kitchen and put away her groceries.

“Who does that?” the sheriff said.

The tragedy that unfolded Monday night had been building for at least two weeks, authorities said, and perhaps even longer. Through interviews taken over the last three days, detectives have discovered details about Steele’s life and those of her children that visibly unnerved Gualtieri in his news conference, including a pattern of “serious behavioral issues” from her two young sons, whom authorities say she often failed to supervise.

There had also been two visits from Child Protective Services.

Steele works as a financial broker at Raymond James & Associates, records show, and her home sits on the intercoastal waterways of the Gulf of Mexico in a neighborhood featuring manicured lawns dotted with backyard pools.

She did not have her first child, the 6-year-old boy, until she was 55. Steele and her late husband, Philip Steele, were featured on the now-defunct reality television series “I’m Pregnant and …” Each episode starred a pregnant woman in an unconventional life scenario: homeless, addicted to drugs, a nudist.

Steele’s hook was her age.

“Kathleen Steele has it all,” says the episode description on Amazon. “A job she loves, a devoted 63 year old husband, a sailboat, beach house; all, except the children she wants. Now, at the age of 55, she’s pregnant with her first child, but nothing about pregnancy at her age is routine or easy.”

She gave birth in 2009, and two years later her husband died of cancer. But before he passed, the couple had his sperm frozen, Gualtieri said. Soon after, Steele paid a doctor in New York City to artificially inseminate her, authorities said, and she had a second son. A few years later, she did it again, and on July 26 of this year, Steele gave birth to a baby girl. She named her daughter Kathleen, after herself.

But just days before her arrival, an accidental fire damaged their home in North Redington Beach, a small community on the Gulf of Mexico, less than 15 miles east of St. Petersburg. The Steele family moved temporarily into the nearby Residence Inn. Three days after baby Kathleen was born, a fire alarm sounded at the hotel in the middle of the night. In the rush to get the children outside, Steele told authorities, she put the infant in a carseat carrier but forgot to buckle it. She tripped down the hotel stairs, Gualtieri said, dropping the carrier on the ground. Her baby tumbled out and hit her head.

Police responded to the scene, but it wasn’t until Steele and the baby arrived at the hospital that the medical staff called the Florida Department of Children and Families child abuse hotline. The baby suffered a minor brain bleed and was admitted to the hospital. Child Protective Services, a division of the Sheriff’s Office, investigated and determined there was no evidence of abuse. The hotel incident “appeared to be accidental,” Gualtieri said.

Steele’s baby was released on July 31 and authorities scheduled a follow-up visit for Aug. 1, just to be sure all was okay. But Steele cancelled, Gualtieri said, and rescheduled the appointment for Aug. 10 — what would turn out to be two days after her child was already dead.

A second call was made to the DCF abuse hotline on Aug. 2, reporting that Steele’s children were “inadequately supervised,” authorities said, though the caller was vague in their reporting. The Sheriff’s Office conducted another investigation, and again found no evidence of abuse.

Less than a week later, on Aug. 8, baby Kathleen’s 13th day of life, Steele took her three children to nearby St. Petersburg. The baby hadn’t been eating properly, Steele said, so she had her examined by a pediatrician. The doctor later told authorities there was nothing medically wrong with the infant and, Gualtieri said in the news conference, “there was no sign of trauma to the baby, the baby’s skull was intact, and there was no bruising on the baby’s face.”

On their way out the door, Steele’s 6-year-old son dropped her phone and cracked the screen, so she left it at the CPR Cell Phone Repair shop and took her children out to lunch.

Surveillance footage shows Steele returning to CPR at 1:50 p.m. She left 38 minutes later.

While she was gone, her children were alone.

The 6-year-old later told investigators that he unbuckled his baby sister from her car seat when she began to fuss, trying to mimic the way he’d seen his mother calm her. Instead he tossed the baby around, slamming her head against the roof of the van and then dropping her on the floor. Authorities later found the girl’s blood smeared on the ceiling.

“Her appearance was one of just a kid that had been pummeled,” Gualtieri said. On the inside, her skull was described as “mush” by the sheriff, fractured like “cracks in a sidewalk.” On the outside, she looked just as bad.

“I’m telling you, this kid’s face was a mess,” Gualtieri said. “There’s no mistaking the condition that this 13-day-old infant was in.”

Yet when Steele returned to her locked vehicle, she did nothing about her injured daughter, according to authorities. Her eldest son said his sister’s injuries were “serious,” the boy told investigators, but his mother ignored him. Instead, she drove to Enterprise to renew the lease on her rented van, something the 6-year-old had reminded her to do.

Gualtieri described the boy as “bright” and “mature above his age,” but deeply troubled with “a lot of pent up hostility and anger.”

“I think Kathleen took this kid at 6 years old and tried to make him a 30-year-old, tried to make him a surrogate father for the other kids,” the sheriff said.

It wasn’t until hours later that Steele told authorities she noticed the baby was purple. She went inside and called a neighbor, a nurse, who called 911 as soon as she saw the child’s condition.

The baby was pronounced dead at a local hospital, but Gualtieri said it’s likely she had died in the cellphone store parking lot.

That night, Steele’s 6- and 3-year-old son’s were taken into protective custody and are currently staying in therapeutic foster homes. Pinellas County Schools told WTSP 10News that the eldest boy will not return to school, but officials there will work with the Sheriff’s Office to create a plan for the child.

“This is a heartbreaking situation,” Superintendent Michael Grego told the TV station. “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.”

Based on their limited interactions with Kathleen Steele and her children, the sheriff said he believes his staff and those with DCF had no way to foreshadow a tragedy like this.

“I can tell you that I’m 100% confident that there’s nothing else we could have done or should have done,” he said.

Through interviews, though, the Sheriff’s Office learned that there may have been warnings signs witnessed by others but never reported to authorities. One neighborhood mom wouldn’t let her son play with Steele’s 6-year-old because he was violent, Gualtieri said, and once the boy sucker-punched an adult.

“If they had brought them forward, maybe something could have been done, maybe not. I don’t know,” Gualtieri said. “You’d need a crystal ball to figure that out.”