STARTED VEHICLE IN PARK WITH RIGHT FOOT ON BRAKE PEDAL. SOON AS PUT IN REVERSE ENCOUNTERED A "SUDDEN UNINTENDED ACCELERATION" (SUA). THROUGH NORMAL REFLEX ALSO HAD PORTION OF MY LEFT FOOT ON BRAKE PEDAL AS THE MOTOR RACED BEING PUSHED IN A BACKWARDS CIRCULAR MOTION BY AN UNKNOWN COMPONENT MALFUNCTION. A 180 DEGREE CIRCLE WAS MADE UNTIL STOPPED BY THE REAR BUMPER OF AN UNOCCUPIED WINDSTAR VAN. THEN I WAS ABLE TO TURN OFF THE IGINITION TO STOP THE STILL RACING MOTOR. THAT WINDSTAR DRIVER HAD JUST DESCENDED FROM HER VEHICLE. THE POLICE HAD MY VEHICLE TOWED BECAUSE OF A VEHICULAR DEFECT. MY VEHICLE MISSED AN OCCUPIED STATION WAGON BY APPROXIMATELY TWO INCHES JUDGING BY SKIDMARKS. THE DRIVER CONFIRMED THAT SOON AS BACK UP LIGHTS CAME ON MY VEHICLE JUST "SHOT OUT" OF THE POST OFFICE PARKING SPACE. MR