WHEN MY DAUGHTER EXITED HER CAR SHE GRABBED HER BACKPACK FROM THE PASSENGER SEAT. ONE OF THE STRAPS FROM THE BACKPACK HOOKED AROUND THE SHIFTER AND MOVED IT TO NEUTRAL. WE DID NOT KNOW THE SHIFTER DID NOT LOCK WHEN YOU PUT IT IN PARK.THE CAR STARTED ROLLING BACKWARD DOWN OUR DRIVEWAY WITH THE DRIVERS DOOR OPEN. THE DOOR CAUGHT ONE OF OUR TREES IN OUR YARD PINNING IT AGAINST THE FRONT FENDER DAMAGING THE DOOR AND FRONT FENDER. SHE HAD HER KEY IN HER HAND SO THE IGNITION WAS NOT ON. AFTER READING ON THE INTERNET SEVERAL OF THESE SHIFTERS ARE DEFECTIVE. THIS IS A DANGEROUS ISSUE THAT GM IS IGNORING. *TR