A Texas mother is behind bars after her two kids were found unconscious in a hot car on a sweltering late summer day and were later pronounced dead, police say.

Tiona Lasaisha Islar, 28, stands accused of two counts of injury to a child in the deaths of her 6-year-old son with autism and 3-year-old daughter, according to the Bexar County Sheriff’s Office in San Antonio. The Bexar County Medical Examiner’s Office identified the children as Miyani Islar and Sevani Stevenson.

Sheriff Javier Salazar told reporters during a press conference that his deputies responded around 3:30 p.m. Saturday to the 7000 block of Chancery Gate for a call about unconscious children. When the first deputy arrived on the scene, he began “simultaneously trying to perform CPR on both children,” but both were pronounced dead.

Deputies took Islar in for questioning.

She told detectives she brought the children inside the home around 10 a.m. on Saturday and believed the kids went back to the car on their own, where she later found them unconscious around 3 p.m., Salazar said. She said she then took the kids back inside before calling 911.

However, deputies are skeptical of her series of events.

“There are just some inconsistencies with the story being given,” Salazar said.

The temperature in the San Antonio area on Saturday was in the low 90s.

Islar was arrested around 7 p.m. Saturday. Salazar said cops had previously been at the home where Child Protective Services responded after concerns about child neglect. He did not expand on the details of the prior interaction.

An injury to a child charge is a second-degree felony, which is punishable by a prison sentence of up to 20 years and a $10,000 fine.

Islar is currently in the Bexar County Jail on a $300,000 bond.