The Park Assist function caused me to have an incident with my vehicle when parking. I safely engaged the autopark function and followed the prompts for the car to proceed with the parking. Suddenly, when reversing the car violently accelerated, making it impossible to brake or stop the collision with the parked car. The Park Assist failed. The safety of pedestrians was put at risk, as people were walking around the area of the collision. Audi has been contacted with no current response to the issue. No warning lights other than the prompt to follow instructions.