EE WAS OPERATING A CAT HAUL TRUCK INT HE AREA WHERE WE WERE DIGGING S UMP WHEN HE STARTED PULLING OUT OF SUMP THE MATERIAL INT HE BED SLID BACK CAUSING THE TRUCK TO STAND UP ON ITS TAILGATE. E E WAS BANGED AGAINST DOOR AND INSIDE OF CAB CAUSING THE LACERATIONS TO HIS HEAD, FACE AND NECK.