I ENTERED MY PARKED, STATIONARY PRIUS, PRESSED MY RIGHT FOOT ON THE BRAKE PEDAL, DISENGAGED THE PARKING BRAKE AND PRESSED THE ON/OFF BUTTON TO TURN THE CAR ON. MY FOOT REMAINED ON THE BRAKE PEDAL. THE ENGINE IMMEDIATELY RACED AND THE CAR BEGAN TO ACCELERATE AT HIGH SPEED. I STOMPED ON THE BRAKE PEDAL AND THE CAR KEPT MOVING. THE SOUND OF THE ENGINE WAS LOUD ENOUGH THAT PEOPLE IN NEARBY HOUSES HEARD IT. MY CAR WOULD NOT SLOW WITH MY EFFORTS TO BRAKE. I TRIED TO SHIFT INTO NEUTRAL AND PARK BUT THE CAR DID NOT SLOW DOWN. IT RACED ACROSS THE STREET AND PLOWED DIRECTLY INTO A NEIGHBOR'S STONE WALL. MY CAR BECAME WEDGED BETWEEN THE WALL AND A LARGE TREE. I HAD TO EXIT THE VEHICLE FROM THE PASSENGER SIDE AS THE DRIVER'S DOOR WAS PRESSED AGAINST THE TREE. AFTER THE COLLISION, INTERIOR LIGHTS WERE NON-FUNCTIONING EVEN WHEN THE DOOR WAS PROPPED OPEN. THE CAR WOULD HAVE CRASHED THROUGH THE HOUSE IF IT HAD NOT BEEN STOPPED BY THE WALL AND TREE.