AT THE TIME OF THE INCIDENT, EE WAS CHANGING HEADS ON THE ENGINE OF A CAT 793C OFF-HIGHWAY TRUCK. AFTER UNBOLTING THE HEAD FROM THE ENGINE, HE PLACED THE INPACT WRENCH ON THE FRAME OF THE TRUC K. AS HE AND A CO-WORKER WERE LOADING THE HEAD ON A CART, THE IMPACT WRENCH FELL OFF THE TRUCK FRAME AND STRUCK EE ON HIS LEFT FINGER.