So apparently Mikey was helping someone else who was in an accident and had stopped to help. What we're told is:

Mike was stopped when a 3/4 diesel driven by a 20 year old never hit the brakes. He had some head trauma but death was caused be a transected aorta. Basically he was hit so hard it ripped the aorta from his heart. Ripped the axle off the car and flipped the car.