Buffalo Grove police and fire units responded to Woodman's Food Market at 1550 Deerfield Parkway just before 3 p.m. for a well-being check on a person inside a vehicle emitting a foul odor.
First responders found a man dead in a blue Chevrolet Equinox parked on the south end of the parking lot.
The man was identified as Danny McCoy, 68, of Skokie by the Lake County Coroner's Office.
The coroner said preliminary autopsy results indicated that McCoy died from natural causes.
A large fire and police presence was on the scene for more than three hours.