I'd say they probably got RAILED by a tractor-trailer, or something of the caliber. Of course, it looks like they got hit, then ran off the road, and had a large rock fall into the bed.
As for parts to salvage, the taillights, rear wheels/tires, the roof marker lights, and maybe a couple of the fender marker lights, but after that, it's one big paperweight.
It looks like they could have gotten out without much harm, though. The cab is rather intact, sort of like what happens when a Saab is in an accident, the exteroir falls apart, but the passenger cabin stays rigid.