trying to figure out how it happened.... i assume they were headed in opposite directions. hard to say who is at fault - one of them must have been over the center line. i've seen people towing trailers and not realizing that the trailer is wider, thus hanging over the line, but in those cases the drivers in the oncoming lanes are generally heading toward the ditch to avoid collision.
looking at the truck & trailer... is it my imagination or is the bumper on the truck twisted upward? was the trailer attached to a ball on the bumper?