Three-year-old twins, Oliver and Aria Orr, were found dead in the family pickup truck on June 18, according to CBS News. The truck was parked in front of the family home in Bossier, Louisiana. Preliminary autopsy results labeled their death as "heat-related," according to KSLA
Officers were called to the scene after their mother found the kids inside the truck. According to neighbor reports, their mother had fallen asleep in the house. When she woke up, she noticed the front door was open and the kids were gone. She enlisted the help of her neighbor, Rhonda Matthews in her search, according to CBS News. During the search, their mother discovered them in the truck. 

Oliver was found in the front seat, his sister in the back. "He was sitting on the floorboard and he had put his head in the seat. I did CPR on both of them," Matthews told KSLA. 

Investigators are still trying to determine exactly what happened. Officers discovered a step stool next to the truck and the children's mother could not tell officers whether the truck had been locked or not. The autopsy revealed no signs of trauma and no charges have been filed, CBS News reported. 

"I can tell you that this was not a case of the children traveling in the pickup truck and somebody just leaving them there and not getting them out. The pickup truck, as far as what detectives know now, was not used that day," City Spokesman, Mark Natale told reporters, according to CBS News. 

The father of the twins is a sheriff's deputy. He was not home at the time of the incident. 

"We are saddened by the tragic loss suffered by the Orr family, and our hearts are heavy. This is a very difficult time, but it's even more so, as they are part of our Bossier Sherriff's Office Family. Please keep Deputy Travis Orr and his family if your thoughts and prayers," the department said in a news release. 

KidsandCars.Org estimates that roughly 38 children per year die after being trapped in a vehicle.