I WAS IN MY DRIVEWAY SITTING STATIONARY IN MY VEHICLE BUCKLING UP TO DEPART FOR THE STORE. I PUT MY FOOT ON THE BRAKE PEDAL TO PUSH THE START BUTTON. AFTER STARTING I MOVED THE SHIFT LEVER TO PUT THE VEHICLE IN GEAR AND THE VEHICLE STARTED TO ROLL AND MY BRAKE PEDAL WENT TO THE FLOOR. BECAUSE MY DRIVEWAY HAS A SLIGHT RAMP TO IT THE VEHICLE KEPT ROLLING FORWARD, I KEPT HITTING THE BRAKE PEDAL BUT THE BRAKE PEDAL KEPT GOING TO THE FLOOR AND THE VEHICLE WOULD NOT STOP. AS A RESULT I ROLLED INTO A BLOCK FENCE ACROSS FROM MY DRIVEWAY KNOCKING IT DOWN AND DAMAGING MY VEHICLE. VEHICLE WAS JUST ROLLING UNDER ITS OWN MOMENTUM, NO POWER TO THE DRIVE TRAIN. NO INJURIES, BUT FENCE WAS DOWN AND VEHICLE HOOD AND OTHER FRONT END AREAS WERE DAMAGED. I HAVE NO IDEA WHAT CAUSED THE BRAKES TO FAIL. FILED AN INSURANCE CLAIM AND HAD TO HAVE VEHICLE TOWED TO DEALER FOR BODY REPAIRS AND NEIGHBORS FENCE REPAIRED.