Rear Seat Belt problems of the 2005 Toyota Camry

I have driven a Toyota Camry for 14 years and have never had an accident nor a traffic citation. In October 2004 we bought a new Toyota Camry. On April 25, 2005 I drove to a meeting at a private home on a 27 acre farm. I had two passengers in the car. When backing up very slowly to turn the car around I had a sudden unexpected speed surge. Brakes did not work. I glanced off one car damaging the back bumper and putting a crease in the side, then hit a pickup truck square on its bumper knocking off the licence plate. Since there were people, cars and buildings behind me, I managed to get it out of reverse but then it surged forward (no brakes) went about 150 ft and I had to turn off the key in an attempt to slow the car down. This was on a long gravel driveway and the car was out of control. It coasted about 90 ft, went through a wire fence, hit a fence post, a roof support, and hit a 800 lb baler which moved 5 ft into a large farm sprayer. Three people witnessed what happened and heard the car when it surged backward. The rear seat belt snapped open on impact. One of the passengers was injured, one had bruises.