GEAR SHIFTED OUT OF PARK TO REVERSE AFTER THE OWNER, LEFT THE ENGINE RUNNING, PLACED THE VEHICLE IN PARK AND EXITED THE VEHICLE TO REPLACE THE GAS CAP. AFTER COLLIDING WITH ANOTHER VEHICLE, THE GEARS SHIFTED FROM REVERSE TO DRIVE AND ACCELERATED FORWARD BEFORE THE OWNER WAS ABLE TO RE-ENTER THE VEHICLE, APPLY THE BRAKES AND STOP THE VEHICLE.