Front Air Bag Sensor Control problems of the 2007 Chevrolet Silverado

I was driving my 2007 Chevrolet Silverado on a highway at approximately 65 mph during a light rain shower when there was a loud bang sound similar to a shot gun blast and the seatbelt pre-tensioners pulled myself and my passenger hard back into the seats. The hazard lights began flashing immediately and the airbag sensor light came on. Contacted onstar to run a diagnostic and they showed there was a collision detected which fired the seat belt pre-tensioners. There was no collision, not even a bump in the road that caused this. This was a very startling event that easily could have caused a panic reaction and an accident. There was a smell of spent gunpowder in the cabin of the vehicle after this occurred. We unlatched our seat belts to relieve the pressure against our bodies and noticed they would not retract or pull back out. They are now useless. The injury was a bruise to my left collar bone where the seatbelt retracted. The vehicle is now not safe to drive since the seat belts don't work and for fear of the airbags deploying.