THE VEHICLE ROLLED BACKWARDS INJURING OPERATOR AFTER IT WAS PLACED IN PARK. OPERATOR MOVED THE AUTOMATIC TRANSMISSION LEVER FROM DRIVE INTO PARK. THE DOORS UNLOCKED AUTOMATICALLY. KEYS WERE IN THE IGNITION. VEHICLE WAS TURNED OFF. OPERATOR EXITED THE VEHICLE. VEHICLE ROLLED BACKWARDS DOWN THE SLIGHT >3% DRIVEWAY. GMC HAS INSPECTED THE VEHICLE AND DONE A DOWNLOAD OF THE ECM. THIS VEHICLE IS DANGEROUS BECAUSE IT EITHER DOES NOT FULLY ENGAGE IN PARK BUT RELEASES THE DOOR LOCKS OR IT SPONTANEOUSLY COMES OUT OF PARK OR SOME OTHER FAILURE MECHANISM.