ON FEB. 10, 2004 CUSTOMER STOPPED AT THE SCALE HOUSE & WEIGHED HIS TRUCK & BELLY DUMP. AT APPROXIMATELY 11:30AM HE RETURNED FOR HIS THIRD LOAD. HE DROVE HIS TRUCK TO BACKSIDE OF EXISTING STOCK PILE. HE SIGNALED LOADER OPERATOR NOT TO LOAD. HE GOT OUT OF TRUCK TO CHECK IF PROBLEM. HE TURNED AIR SWITCH ON & GOT PRY BAR TO OPEN GATE. THE GATE RELEASED & EJECTED PRY BAR INTO CHIN/NECK.