A Michigan State Police Trooper was killed Wednesday on I-75.

Trooper Joel Popp of the Tri-City Post, near Midland, was struck by a motorist while standing outside of his vehicle. Popp was in the process of investigating a suspected impaired driver at the time. He became the 56th Michigan State Trooper to be killed in the line of duty.

The State Police say the crash happened shortly after 7 pm Wednesday evening when an 81 year-old driver struck two police cars, as well as Trooper Popp. The other driver had serious injuries but was expected to survive.