EMPLOYEE STATED HE WAS HELPING UNLOAD LARGE BAGS OF ROCK DUST FROM TRACK CAR TO SCOOP BUCKET. EMPLOYEE HAD CUT THE BAG ONCE IT WAS LOADED IN SCOOP AND WAS TRYING TO REMOVE IT. EMPLOYEE WAS PUL LING ON THE BAG WHEN IT CAME LOOSE CAUSING HIM TO FALL BACKWARD LANDING ON HIS LT. SHOULDER. HIS FIRST LOST WORK DAY DID NOT OCCUR UNTUL 10/2/03.