Wheel Bolts problems of the 1999 Jeep Grand Cherokee

Somehow a wheel popped off of my 1999 Jeep Grand Cherokee that I bought used from a certified Jeep dealer a year and a half ago (2002). I am unsure how this happened, but all 5 lug nuts broke off, causing the wheel to completely pop off. Luckily, I wasn't driving more than 10 mph when this happened. I have never taken my car in to get fixed for anything during the time I owned it. I have taken it in for oil changes and responded to a couple recalls on my car, but that's it. The last mechanic who touched this car was from the Jeep dealership where I bought it. Currently, the car has 37,000 miles on it. As I said before, I am unsure how this happened. I haven't been in an accident, haven't hit the wheels on anything, haven't rotated the tires, etc. This is a major safety concern for all Jeep owners. I'm currently working with the Jeep dealership to figure this out and I plan on contacting the manufacturer ASAP. I want to sure this doesn't happen to me again and I want to be sure other drivers are not at risk.