Police were called to the home on Tipton Highway in Clinton Sunday afternoon.
It appears the child, Jonathan Kaufman, found the loaded .40-caliber handgun in a closet. He was alone inside the home while his father and brother were outside.
Police say the child somehow pulled the trigger, and shot himself in the head.
Michigan State Police are investigating the death. A report will be sent to the county prosecutor's office for review, which typically happens in such cases.
Clinton, Mich. is in Lenawee County, approximately 60 miles southwest of Detroit.