Two young children in Tulsa, Oklahoma, died after spending five hours inside a locked truck on a 90-degree day, police said, and now, their father has been arrested for murder.

Dustin Lee Dennis, 31, is facing two counts of second-degree murder for the deaths of his 4-year-old, Teagan, and his 3-year-old, Ryan. Around noon on Saturday, he told police, Dennis drove with his kids to a convenience store and then returned to his house.

Dennis claims that he then fell asleep for four or five hours, and when he woke up, he didn’t know where his children were. He eventually found them in the floorboard of his truck, and the two were pronounced dead when the paramedics arrived on the scene.

“The children had not been checked on for nearly five hours during the time they were locked inside vehicle,” police said in their arrest report.

On hot or even mild days, the National Safety Council warns, the insides of cars get reach life-threatening temperatures. More than 800 children have died from heatstroke in vehicles over the last two decades.

Dennis is currently being held on bond in the Tulsa County Jail.