The state patrol says a trooper pulled a truck over on Highway 48 near Cumberland Sunday morning for speeding.
The driver was 38-year-old James Milliman from St.Croix Falls.
After talking to him and returning to his squad car, the trooper heard a gun shot come from the truck.
After backup arrived, troopers approached the truck and discovered Milliman had shot himself in the head with a handgun.
He was taken to Cumberland Hospital and then flown to a Minnesota hospital where he later died.
Milliman was expected in court Monday on drug related charges.