WAITING IN LINE AT COSTCO TO GET FUEL. PULLED APPROX 2 TO 3 FEET FROM VEHICLE IN FRONT. I ENGAGED THE AUTO PARKING BRAKE WHILE WAITING. NEXT THING THE BRAKE DIS-ENGAGED AND CAR LUNGED FORWARD HITTING THE CAR IN FRONT OF ME AND THE CAR IN FRONT OF THAT VEHICLE BEFORE I HAD TIME TO HIT THE BRAKE. DAMAGE TO LEXUS IS $7000 NO ESTIMATES ON DAMAGE TO OTHER CARS. OTHER DRIVERS REPORTED AND GETTING MEDICAL ATTENTION.