At approximately 9:18 p.m. Thursday night, a trooper with the Missouri Highway Patrol observed a vehicle parked on the shoulder of U.S. 54 near Mo. Rt. BB in Callaway County.
The vehicle had its lights on and doors open.
As the trooper approached the car, he observed a subject, later identified as Joseph Cockrum, 25, of Fulton, rolling in the grass.
After making contact with Cockrum, he became aggressive and began experiencing medical problems.
Troopers requested assistance from emergency medical services and began CPR.
Cockrum was transported to Callaway County Community Hospital where he was pronounced deceased.
An investigation is being conducted by the patrol's division of drug and crime control.
An autopsy was scheduled for Friday at the Boone County Medical Examiner's Office.
There was no word on how soon results from the autopsy would be known.