A man was killed when his snowmobile struck a tree in Whitewater Township Tuesday, according to the Walworth County Sheriff’s Office.

Deputies were called to W9215 State Highway 59 at 11 p.m. Tuesday and found an unresponsive man on a snowmobile that had struck a tree.

Investigators said Michael H. Zielinski, 37, of Whitewater Township, was riding the snowmobile on the property without a helmet.

Emergency responders performed CPR, but Zielinski was pronounced dead at the scene.