VEHICLE WAS IN PARK AND IDLING. WHEN PUT INTO REVERSE,THE ENGINE RACED FULL THROTTLE AND CAR CRASHED INTO CANS. WHEN PUT INTO WHAT APPEARED TO BE PARK,CAR TOOK OFF FORWARD WITH TIRES BURNING SO MUCH SMOKE, VISIBILITY WAS IMPOSSIBLE.CAR WAS UNCONTROLLABLE AND CRASHED THROUGH WOODED AREA INTO A TREE. ENGINE WAS STILL RACING AND DID NOT STOP UNTIL IGNITION KEY REMOVED. FOOT WAS NEVER ONCE ON THE ACCELERATOR. SEEMED THROTTLE WAS SOMEHOW STUCK WIDE OPEN. SPEED UNCERTAIN AS IT WENT APPROX 200 FT BEFORE CRASHING AND TIRE SMOKE WAS SO THICK. THREE PEOPLE WITNESSED INCIDENT.