I HAD PULLED OUT OF A PARKING PLACE AND WAS WAITING IN THE TRAFFIC LANE TO EXIT THE AREA. THERE WERE TWO CARS IN FRONT OF US. THE CARS WERE STOPPED. I WAS APPROXIMATELY 20-25 FEET BEHIND THE CAR IN FRONT OF ME. I TOOK MY FOOT OFF THE BRAKE IN MY CAR TO LET IT IDLE FORWARD. AS I APPROACHED THE YUKON I REAPPLIED THE BRAKE. THE CAR ACCELERATED TO WHAT SOUNDED LIKE FULL RPM'S AND I APPLIED THE BRAKES AS HARD AS I COULD AND NOTHING HAPPENED. THE CAR SLAMMED INTO THE YUKON WITH SUCH AN IMPACT THAT BOTH FRONT AIRBAGS DEPLOYED. THE DRIVER SIDE AIRBAG HIT ME IN THE FACE. THE PASSENGER AIRBAG DID NOT REACH MY WIFE IN THE PASSENGER SEAT. SHE IMMEDIATELY EXPERIENCED SEVERE CHEST PAIN AND RAPID HEART BEAT. BYSTANDERS CALLED 911 AND TWO PARK RANGERS ARRIVED IN APPROX. 15-20 MINUTES. THE RANGERS FINISHED TAKING PICTURES AND ASKED ME TO PULL IN TO A PARKING SPOT OUT OF THE TRAVEL LANE OF THE PARKING LOT. I STARTED THE CAR AND PROCEEDED SLOWLY AND TURNED INTO A PARKING SPOT. AS I APPLIED THE BRAKE TO PARK, THE SAME PHENOMENON OCCURRED AGAIN. THE CAR ACCELERATED FORWARD OVER A CURB AND WALKWAY AND STRUCK A PEDESTRIAN BEFORE COMING TO A STOP ON A RETAINING WALL. I DESPERATELY TRIED TO STOP THE CAR WITHOUT SUCCESS. THE EMS WAS THERE SHORTLY AFTER THIS OCCURRENCE. A RANGER ASKED ME HOW FAST I WAS MOVING AND I STATED I HAD NO IDEA. I ASKED HIM TO ASK THE RANGER WHO WAS RIGHT BEHIND ME AND HE SAID 5 MPH. I EXITED THE VEHICLE AFTER THEY TRANSPORTED THE PEDESTRIAN ON THE BAC