I was exiting a parking spot and I had my foot on the brake to start the vehicle and again to put the car in reverse. I backed out of my parking spot and turned 90 degrees to exit the parking lot. As I pushed down on the brake to stop and shift to drive, the pad that covers the brake pedal fell off, causing my foot to slip and hit the accelerator. I then struck another vehicle with the back of my car. In looking at the car after the accident, the pad that normally covers the brake pedal was on the floor of the car, between the brake and accelerator. At the body shop, one of the people said there is supposed to be a clip that holds the pad, but it was either broken or missing on my car.