PUT TRUCK INTO PARK TO HELP TRUCK AHEAD OF US UNLOAD BED. OUR TRUCK WAS IN PARK WITH ENGINE ON, WITHIN 3 MIN TRUCK BEGAN ACCELERATING AND CRUSHED BODY IN BETWEEN TWO TRUCKS. HAD TO PRESS BREAKS (CAR STILL ROLLING) SHIFT INTO REVERSE, BACK INTO PARK BEFORE CAR WOULD STOP ROLLING THEN WENT INTO REVERSE. *TR