SPOUSE PARKED IN FRONT OF A STORE.PUT IN PARK, SIT THERE AWHILE FILLING OUT PAPERWORK AND THEN WENT INSIDE. SLIGHT INCLINE TO REAR OF VEHICLE. WHEN DRIVER GOT OUT, LEFT PASSENGER IN VEHICLE.PASSENGER HEARD POP AND VEHICLE STARTED ROLLING BACKWARDS. PASSENGER SCARED AND DEPARTED VEHICLE AND DRAGGED SEVERAL FEET.(TOOK PASSENGER TO HOSPITAL LATER) VEHICLE CONTINUED TO ROLL UNTIL CONTACT WITH TREE PREVENTING IT FROM JUMPING CURB INTO STREET. APPARENTLY VEHICLE POPPED OUT OF PARK INTO NEUTRAL. PREVIOUS COMPLAINT TO DEALER ABOUT AUTO JUMPING FORWARD AT STOPS AND BRAKES APPLIED TO PREVENT COLLISION WITH AUTO IN FRONT. THEY REPORTED NO TROUBLE FOUND. INFORMED ON THEM MORE THAN ONE OCCASION THAT IT WAS INTERMITTENT. VEHICLE WAS DOING THAT VERY SAME THING VERY BADLY PRIOR TO INCIDENT. DUPLICATED SCENE WITH MY VAN AND AS SOON AS I PUT INTO NEUTRAL IT IMMEDIATLY BEGAN TO ROLL BACKWARDS. THIS IS AN UNSAFE VEHICLE!*AK