PARKED IN THE DRIVEWAY WHICH IS ON A SLIGHT UPWARD INCLINE WITH CAR RUNNING, UNLOADING GROCERIES WHILE KIDS WERE WATCHING A VIDEO. AFTER 15 MINUTES I REACHED IN THROUGH THE PASSENGER SIDE TO TURN OFF THE IGNITION AND THE CAR RELEASED OUT OF PARK, ROLLING DOWN THE DRIVEWAY, HIT A TREE AND MAILBOX. VEHICLE WAS 'CLICKING' THE ENTIRE WAY DOWN THE DRIVEWAY. *JB