As Jo*Mar said, this could cause a whiplash like neck strain. It would not cause a brain injury.

The car could have transmission damage to a part called the Park Pawl. Park may not work properly, like when the car is parked on a hill. The transmission should be checked for proper function of Park.

Park does not apply the brakes. It just puts the transmission in Neutral and locks the Output Shaft so it will not turn.

How do you know the speed was 11 mph ?