A 13-month-old baby died of heatstroke on a chilly January day in North Georgia after his grandmother left him in her car for five hours while she visited with friends, authorities said. They said the car and heater were running.

Barbara Michelle Pemberton, 47, was charged Friday with second-degree murder and child cruelty, said Greg Ramey, special agent in charge of the GBI office in northwest Georgia. Ramey said Pemberton told her friends when she arrived at their house in Walker County that she didn’t want to wake her grandson, so she left him sleeping in his car seat. She was watching the baby for her son.

But when Pemberton returned to her car around 4 p.m. Tuesday, five hours later, Shadoe Braxton Pate was not breathing. He was dead in his car seat, Ramey said.

Ramey said the sun pouring in through the windows and the hot air blasting from the heater made the inside of the car as hot as “a summer day,” well over 100 degrees. The autopsy showed the cause of his death was hyperthermia, exposure to extreme heat over a period of time.

Pemberton, who was being held in the Walker County Jail on a $100,000 bond, had “been cooperative for the most part,” Ramey said. “She was up front about her role with the child. But obviously, through the investigation, it was determined that, regardless of how forthcoming she was, she was neglectful of the child.”

The second-degree murder charge comes from a law passed by the Legislature in 2014. Republican state Rep. Christian Coomer of Cartersville, the sponsor, has said he crafted the statute because of discrepancies in how various law enforcement agencies were charging when a child had died in a hot car.

Prior to the second-degree murder law, police typically charged people whose children died in a hot car with involuntary manslaughter, which carried a maximum punishment of 10 years in prison. The punishment for second degree murder is 10 to 30 years in prison, and there is no requirement for prosecutors to show intent.

Justin Ross Harris, the Cobb County man who will stand trial this spring in the hot-car death of his toddler son, is charged with malice murder, indicating that police believe he intended for his son to die.

Last year 24 children nationwide died of heatstroke after they were left in cars, usually in the summer. Shadoe’s death is the only one so far this year, according to Department of Meteorology & Climate Science at San Jose State University, which tracks cases of children dying because they were left in hot cars. Thirty-one children died in hot cars in 2014 and 44 died in hot cars in 2013.

San Jose State University said 51 percent of the time the children were “forgotten” by a caregiver, 21 percent of the time a child was playing in an unattended vehicle and 17 percent of the time an adult intentionally left the child in the car.

Ramey said the friends she was visiting suggested several times that she check on the baby, but she “never left the residence.”

Walker County Sheriff Steve Wilson could not be reached late Friday but he told Chattanooga television station WRCB earlier Friday Pemberton’s friends said the grandmother would occasionally look out the window but the car was parked too far away for her to clearly see Shadoe.

“I guess it’s obvious, for whatever reason, she chose not to go back out and check on him, which is difficult to understand and comprehend,” Wilson said, according to WRCB.