CONSUMER WAS UNDER THE IMPRESSION THAT THE VEHICLE WAS IN PARK . AFTER LEAVING THE VEHICLE RUNNING VEHICLE SLIPPED INTO REVERSE AND ROLLED BACKWARDS,COLLIDING WITH A VEHICLE BEHIND IT. WHEN THE GEAR SHIFTER WAS PUT IN PARK CONSUMER WAS UNAWARE THAT THE SHIFTER NEEDED TO BE HOOKED OVER AND SEATED TO THE RIGHT. THERE WERE NO INJURIES INVOLVED. POLICE ARRIVED, BUT,NO ONE WAS CITED. *AK