CRUISE CONTROL SWITCH WAS ON BUT NOT ENGAGED. I PULLED UP TO BACK INTO PARKING SPACE, AND WITH MY FOOT ON THE BRAKE PEDAL, THE TRUCK LUNGED FORWARD INTO PARKED CARS. THE TRUCK STOPPED, I PUT MY FOOT BACK ON THE BRAKE PEDAL, LOOKING TO MAKE SURE I WAS ONLY ON THE BRAKE PEDAL, AND THE TRUCK LUNGED FORWARD AGAIN INTO PARKED CAR. I TOOK MY FOOT OFF OF BRAKE PEDAL, PUT THE SHIFTER IN REVERSE, AND THE TRUCK TOOK OFF AT HIGH SPEED IN REVERSE, CLIPPED A FIRE HYDRANT, AND STOPPED ABOUT 100 FEET AWAY, BACKING INTO AN EARTHEN BANK. ALL OF THIS OCCURRED IN THE PARKING LOT AT MY PLACE OF WORK.