HAD JUST PUT VEHICLE (LEASED) INTO PARK POSITION WITH THE ENGINE RUNNING. LEFT VEHICLE FOR A SHORT WHILE. WAS INFORMED, BY A WITNESS, THAT VEHICLE HAD BUCKED AND THEN STARTED ACCELERATING, FAST, BACKWARDS. VEHICLE THEN HIT ANOTHER VEHICLE THAT WAS PARKED. CONTACTED MANUFACTURER AND INFORMED WILL BE SENDING AN INDEPENDENT INSPECTOR TO CHECK ON VEHICLE. MR