NHTSA Complaint #11473152 — 2015 GMC SIERRA 1500

My truck has just over 54,000 miles on it. I bought it new and have treated it well. It's my "Sunday" truck. Without warning, yesterday while carrying my wife to a doctor's appointment, as I pulled into a parking space to park ... I had almost no brakes. I actually jumped on the emergency brake to aid me in getting stopped. After my wife had gone in for her appointment, I slowly moved the truck around the open areas of the parking lot trying to figure out what the problem was. I checked the brake fluid, looked to make sure I hadn't lost a brake pad or something else weird and found that everything was good. What I did find though was that the only time the truck had any issue was when I was moving under maybe 4 or 5 mph. And in fairness ... I discovered the truck did have some tiny (but I do mean tiny) amount of braking ability at that low speed, but to say that the experience was unnerving would be a terrible understatement. Had someone been standing between me and the vehicle I was parking in front of when I experienced this, there is absolutely no doubt in my mind that I would have pinned them between our vehicles, or God forbid, something worse. I don't know what's going on here, but there's definitely something going on with the brake system at low speed on this GMC.