EMPLOYEE LOOKED UP & SAW THAT THE JAW WAS NOT MOVING; ROCKS WERE BACKED UP ALL THE WAY TO TOP OF SCREEN. HE SIGNALED FOR THE LOADER OPERATORS TO KILL THE SCREEN PLANT. THEY DID NOT. HE CONTINUED ON TO THE SCREEN PLANT TO ATTEMPT TO GET IT GOING AGAIN. WHILE TRYING TO GET JAW RUNNING A ROCK CAME OFF THE SCREEN PLANT BETWEEN SHAKER & SHOOT AND HIT HIM ON TOP OF THE HEAD.