A major medical problem is to blame for a man dying after he drove off the road and landed upside down in a river Friday.

Chippewa County Corner Kay Gerrits says 58-year-old Thomas Tillman of Eau Claire had a severe diabetic reaction while he was driving.

She says that is what caused him to lose control of the pest control truck he was driving and crash into the Yellow River in Cadott.

Gerrits says an autopsy was done Friday and the cause of death was drowning.

Witnesses say his pest control truck slammed through an electric fence, drove through a field and landed upside down in a river.

Gerrits says Tillman was wearing his seat belt.