As I understand it, the two guys in the minivan were loading the recovered dirtbike into it; they were going to just leave.
Just as some towns leave crashed cars in front of the police station with DUI warnings, this town should leave the bloody mangled bike as a theft warning.
So they were loading it into the van and the owner misjudged his braking distance - in his excitement at finding his stolen bike - and ran into the back of the bike and them?