St. Joseph police say the 39-year-old man reportedly told coworkers he wasn't feeling well and wanted to go rest in his van parked in the company lot.
Shortly after midnight, security found the man in his car and called police. He was pronounced dead at the scene.
The man's body was taken to Topeka, Kan. for an autopsy.
Capt. Jeff Wilson said detectives do not suspect foul play.