CAR WAS SLOWLY PULLING INTO A PARKING SPOT, WHEN ALL OF A SUDDEN IT REVVED ITS ENGINE AND ACCELARATED. MY FOOT WAS ON THE BRAKE AND IT WOULD NOT STOP. THE REVVING NOISE WAS LOUD. I HIT A LARGE TREE THAT WAS LUCKILY AT THE END OF THE PARKING SPOT. THE TREE IS WHAT STOPPED THE CAR. WHEN THE CAR STOPPED, I LOOKED AND SAW WAS IN DRIVE. I WAS ABLE TO PUT IN REVERSE AND BACK UP AND PARK SAFELY. I SHUT THE CAR OFF IMMEDIATELY.