A Marthasville man sustained serious injuries Monday night when the motorcycle he was on struck a deer.

Chad A. Williams, 39, was on a 2006 Honda VT600 at 7:52 p.m. on Highway AJ south of Highway YY when a deer ran into the roadway, according to a Missouri State Highway Patrol preliminary report. 

The motorcycle struck the deer, overturned and left the road.

Williams was flown by air ambulance to Mercy Hospital St. Louis. He was not wearing a helmet, the patrol said.