2008 GMC YUKON XL 2500

THIS NEEDS TO BE LOOKED AT BY GM. MY UNCLE HAS A 2008 GMC YUKON XL 4WD. WHEN IT IS PUT IN PARK IT WILL ROLL AWAY ON ITS OWN. WE FIRST NOTICED IT ABOUT 3 WEEKS AGO, BUT THOUGHT IT HAD TO BEEN THAT IT WAS ON ICE OR SOMETHING AND IT ROLLED ABOUT 40-50 FEET BACK. WELL LAST SATURDAY I WAS HELPING TO UNLOAD GROCERIES OUT OF IT WITH MY MOM AND UNCLE. JUST AS I PULLED THE LAST BAG OUT IT ROLLED BACK. I SEEN THE TIRES ROLLING. IT ALMOST RAN ME OVER, BUT I MOVED JUST IN TIME TO HAVE IT KNOCK ME ON TO MY K

Mileage: 25,000