Police determined an 11-pound rock from the back of a semi-truck crashed though a driver's windshield, causing him to crash his vehicle.

Rescuers responded just after 8:50 a.m. Monday, Oct. 17, to the scene south of Turner Avenue and West River Drive NW, where a man was found unconscious.

The man, identified as a 48-year-old Grand Rapids resident, crashed into a power pole and swiped a building, according to a news release. An 11-pound rock, about 8x7 inches, hit him in the head just prior to the crash.

It's believed it fell from a white non-sleeper cab semi-truck with a black dump trailer traveling southbound on Turner Avenue.

Anyone with more information is asked to contact the Walker Police Department.