VEHICLE WAS IN PARK ON A FLAT STREET. I WANTED TO MOVE THE VEHICLE FORWARD, SO I DEPRESSED THE BRAKE, AND BEGAN SHIFTING THE (AUTOMATIC) SHIFTER TO DRIVE. THE GEAR SHIFT LEVER NEVER MADE IT TO THE DRIVE POSITION. AS I MOVED THE LEVER, THE CAR SHOT BACKWARDS, STRIKING A VEHICLE BEHIND ME WITH TREMENDOUS FORCE. I HAVE HAD THE SAME MODEL CAR FOR OVER 7 YEARS AND NEVER HAD THIS HAPPEN. I CANNOT FIGURE OUT HOW OR WHY THE CAR ACCELERATED (FORCEFULLY) IN REVERSE AS I WAS SHIFTING INTO DRIVE. *TT