I PLACED THE VAN IN PARK AND LEFT IT RUNNING AT THE TOP OF A DRIVEWAY WALKED ABOUT 40-60FT AND ABOUT 3 MINUTES LATER IT COMES ROLLING DOWN THE DRIVEWAY AND HITS THE CORNER OF HOUSE AND ME. BOUNCES BACK 23 FEET AND STOPS. GEAR SHIFT IS STILL IN PARK AND CAR IS RUNNING. AIR BAG INFLATES AND ALARM GOES OFF. TURNED OFF ENGINE AND REMOVED KEY.