VICTIM WAS DRIVING A HAUL TRUCK. A ROCK GOT HUNG IN THE TAIL PULLEY OF CONVEYOR #3. VICTIM PARKED TRUCK AND PROCEDED OVER TO CONVEYOR #3, WHILE WAITING TO SHUT DOWN TO REMOVE THE ROCK FROM CONVEYOR #3 A ROCK FELL FROM CONVEYOR #4 HITTING VICTIM IN THE BACK OF THE HEAD.