I WAS PARKED. I STARTED THE CAR AND PUT IT IN REVERSE TO MOVE IT CLOSER TO A BUILDING, FROM ONE SIDE OF A DIRT DRIVEWAY TO THE OTHER. WHEN I STARTED BACKING UP EVERYTHING SEEMED FINE BUT AFTER A FEW, MAYBE 3 SECONDS, THE ENGINE STARTED ROARING AND THE CAR TOOK OFF AT TREMENDOUS SPEED. I DON'T KNOW HOW FAST THE CAR WENT.I HIT THE BUILDING, THAT'S WHAT STOPPED THE CAR. I DON'T KNOW IF IT WOULD HAVE STOPPED OTHERWISE.