AUGUSTA, Mo. (AP) — An eastern Missouri man is charged with leaving the scene of an accident that cost a motorcyclist his leg, and the victim’s son is being credited with tracking down the suspect.

Authorities say 32-year-old Christopher Wirstrom of Augusta was arrested Monday after D.J. Helfert used evidence at the crash scene and traced it to Wirstrom’s car.

Daniel Helfert’s motorcycle was struck on Highway 94 in St. Charles County on Monday, sending it off the road and into a ditch. One of Helfert’s legs had to be amputated.