ROTARY CONTROLLER FOR GEAR WAS IN PARK POSITION. DRIVER EXITED THE VEHICLE WITH DRIVER DOOR OPEN AND BOTH FEET ON GROUND WHEN VEHICLE SUDDENLY SHIFTED INTO REVERSE GEAR. DRIVER WAS UNABLE TO JUMP BACK INTO VEHICLE TO PRESS ON BRAKES AND WAS FORCED UNDER THE OPEN VEHICLE DOOR. OCCUPANTS INCLUDING A BABY WERE IN THE BACK SEAT. VEHICLE CRASHED INTO A BUILDING WITH DRIVER DOOR IMPACT BENDING FORWARD TO SLOW THE CRASH BEFORE STRIKING A TREE AND COMING TO STOP. VEHICLE IS A TOTAL LOSS WITH FRAME AND ROOF DAMAGE, PILLAR DAMAGE EXTENSIVE FRONT/SIDE AND REAR DAMAGE, DOOR WAS NEARLY TORN OFF HINGE.