I slowly put my foot on the brake and suddenly heard a noise under the vehicle. It sounded like loud grinding. As pulled forward I looked in the rear view mirror and didn't see anything in the road that may have fallen out from under my vehicle. When I pushed on the gas I was suddenly accelerating forward very quickly without my control. This was maybe one or two seconds after I heard the noise. I hit the brakes and nothing happened. My only choice was to hit the back end of the other vehicle as there were pedestrians on either side. The vehicle was continuing to accelerate even after I tried to put it in park. I was worried if the car in front of me moved, that I would keep going. I even pressed the emergency brake button twice and nothing worked. Nothing was working at all. I called the police. They told me to try turning off the car. I pressed the button to turn the car off, but it took several pushes to work. I could hear that the rpms lowered extremely slowly. Once the police came they didn't see anything in the road at all. Vehicle was moved to a body shop and when they turned on the car it immediately started revving really loudly again.