WHILE CLEARING A STORAGE BIN WITH A SKID STEER LOADER, THE OPERATOR STOPPED THE MACHINE LIFTED THE BUCKET APPROX 1/4 OF THE WAY UP. HE CLIMBED OVER THE BUCKET ONTO THE WALL OF BIN, THREW 2 STONES INTO THE BUCKET, HE THEN JUMPED TO THE FLOOR OF BIN & STARTED TO GET BACK INTO LOADER WHEN HIS FEET PRESSED THE LIFT CONTROL PEDAL CAUSING LIFT ARMS TO LOWER, PINNING OPERATOR