Automatic Transmission problems of the 2003 Buick Regal

The contact stated after putting the vehicle in park, the vehicle jumped into reverse on its own slamming the contact between the driver's side door and a chain link fence. The contact suffered injuries to the left leg and calf and a broken right foot. The dealership has not been contacted yet. The vehicle was towed to a body shop. There was damage done to the vehicle and to the chain link fence. On one other occasion the vehicle jumped out of park and tried to go forward, but the contact was able to stop the vehicle in time.

(1) I have a 2003 Buick Regal with mileage of 17700. This morning at 9 am when I stopped before the traffic light in the intersection of mound rd and 13 mile rd. (2) suddenly the brake pedal appears to be very loose and the car starts going backward slowly. I keep on pressing the brake but the car keeps going backward. I switched to parking gear and then driving gear and press the gaspedal and the car starts moving forward. Both my wife and I were in the car. Fortunately no car was behind us so no accident occured. (3) the dealer checked the car and can not find what is the problem. So they asked us to continue driving until the problem happens again! how can we continue driving a car which almost led to a fatal accident? that is crazy!.