VEHICLE PARKED IN LOT ON 8-18-16. WHEN WE CAME OUT OF STORE, THE TAHOE HAD ROLLED INTO ANOTHER SPOT. TWO CARS WERE DAMAGED. INCIDENT ON TAPE AT THE WALMART STORE. POLICE REPORT WAS FILED. TAHOE WAS IN DRIVE. TWO OF US HAD EXITED THE VEHICLE AND COLLECTED SEVERAL SHOPPING CARTS, SO PEOPLE WOULD NOT DAMAGE THEIR VEHICLES. THIRD PERSON EXITED THE VEHICLE. IF LEFT IN DRIVE, (ELECTRIC START) NO BELLS OR ALARMS WENT OFF. DOORS WEREN'T LOCKED AS PERSON IN BACK SEAT WAS ABLE TO EXIT. WE WERE IN THE STORE FOR ABOUT 15 MINUTES. ON VIDEO, THE TAHOE WAS IN ITS SPOT FOR QUITE A WHILE BEFORE ROLLING BACK. MY WIFE HAD THE VEHICLE AT THE TIME OF THE INCIDENT. THERE WERE SEVERAL WITNESSES.