WHILE LOADING WITH 992G IN STRIP PIT, A ROCK ROLLED OUT OF THE SHOT BEHIND THE RIGHT FRONT TIRE, CAUSING THE LOADER TO RAISE UP AND TILT TO THE LEFT. TO KEEP THE LOADER FROM TURNING OVER, HE D ROPPED HIS BUCKET TO THE GROUND. THE SUDDEN SHIFTING OF THE LOADER FROM SIDE TO SIDE CAUSED THE OPERATOR TO STRIKE HIS HEAD ON THE LEFT SIDE OF CAB.