BOONE COUNTY, Ind. -- An Indiana State Trooper was seriously injured when he was struck by a vehicle while conducting a traffic stop on I865 Wednesday morning.

Trooper Ronneal Williams conducted a traffic stop on a van near the 4-mile marker.

A Ford Fusion traveling eastbound went off the shoulder of the road and struck the rear of Williams' patrol vehicle. The force of the crash pushed the patrol vehicle into the van.

When the van was hit, it struck Trooper Williams and he went airborne over a guard rail.

Williams used his radio to call for help.

Williams and the other two drivers were all transported to the hospital.

Investigators are trying to determine why the driver of the Ford Fusion went off the side of the road. If you witnessed this crash or the moments leading up to the crash, please contact the Indiana State Police at 317-899-8577.

Williams is in critical condition, but is stable. The injuries to the other drivers are not believed to be life threatening.