STOPPED THE VEHICLE, PLACED INTO PARK POSITION, SHUT OFF CAR AND ENGAGED EMERGENCY BRAKE. REMOVED SEAT BELT, DRIVER AND PASSENGER OPENED DOORS TO EXIT. ENGINE AT THAT TIME WENT INTO A VERY HIGH RPM MAKING A HORRIBLE LOUD WHINING NOISE AND AUTO ACCELERATED IN REVERSE WITH CAR IN PARK AND EMERGENCY BRAKE ON. TRIED TO STOP THE VEHICLE BUT BRAKE PEDAL WENT TO FLOOR. NO CONTROL OF THE VEHICLE AND RODE THE VEHICLE AS IT REVERSED ON ITS OWN, ONTO STREET, THROUGH THE INTERSECTION ,COLLIDING WITH A PARKED CAR AND COMING TO REST WITH THE REAR OF THE CAR AGAINST A BUILDING. SPEED UNKNOWN, NO AIRBAGS DEPLOYED, SMALL INJURIES. *TR