VICKSBURG, Mich. (WOOD) — A father has been charged in the death of his 3-year-old son, who was left in a hot car near Vicksburg in August.

Chad Martin, 36, of Athens, Michigan, was charged with leaving a child in a vehicle causing death, the Kalamazoo County Prosecutor’s Office confirmed Tuesday. If convicted, Martin could face up to 15 years in prison.

The child was discovered dead in his father’s SUV on the afternoon of Aug. 13 at a Family Fare in Vicksburg. Police reports from the Kalamazoo County Sheriff’s Office obtained by News 8 show his father told investigators he didn’t know what happened that day.

“I guess I went straight to work,” the report says he told investigators when he was interviewed.

The father arrived at his job at a plant in Brady Township, just outside of the Vicksburg limits, around 6:40 a.m., the reports show. He left around 3 p.m. and then stopped by the Family Fare afterward to get groceries. He was inside for a few minutes and when he came out, he realized his son was still in the car, buckled into in a rear-facing car seat in the driver’s side back seat. The boy was dead by then.

The father started crying, the police reports show. A bystander told a store worker to call 911.

The death was believed to have been the result of prolonged heat exhaustion. The police reports noted a temperature of 83 degrees, and Storm Team 8 says the high in the area that day was 84.

The father told investigators nothing was different about the family’s routine that day. He said he wasn’t running late, he had been sleeping normally and he doesn’t use sleeping aids or recreational drugs or drink.