WHILE IN REVERSE WITH FOOT ON BRAKE (STOPPED) THE VEHICLE WAS REAR ENDED. WHILE FOOT STILL ON BRAKE THE VEHICLE HAD UNCOMMANDED FORWARD ACCELERATION (ENGINE REVVED UP LIKE FOOT FLOORED THE GAS PEDAL). VEHICLE ACCELERATED FORWARD ~25 FT AND HIT THE FRONT OF ANOTHER VEHICLE (FOOT ON BRAKE PEDAL ENTIRE TIME). UPON IMPACT, THE VEHICLE HAD UNCOMMANDED ACCELERATION IN REVERSE (FOOT ON BRAKE PEDAL STILL). WAS ABLE TO TURN OF IGNITION AND PULL THE EMERGENCY BRAKE TO STOP THE VEHICLE AFTER MOVING ~25FT IN REVERSE. AT FINAL STOP, THE VEHICLE'S TRANSMISSION LEVER WAS IN THE DRIVE POSITION. NOTE: TOW TRUCK DRIVER STARTED VEHICLE TO GO IN REVERSE A FEW FEET FOR POSITIONING. WITH ENGINE RUNNING, VEHICLE WAS PUT IN REVERSE AND GAS PEDAL PRESSED GENTLY. VEHICLE WENT IN REVERSE (< 2MPH) AS IT SHOULD. FOOT APPLIED TO BRAKE AND VEHICLE PUT IN PARK IN ONE MOTION. VEHICLE IN PARK AND FOOT ON BRAKE THE ENGINE BEGAN TO REV UP AGAIN. KEY WAS TURN OFF. VEHICLE TOWED.