What affect could this have had on my automatic transmission?

Ok so I was parked on a hill and the car engine was off, then without starting the car I shifted to reverse (I thought the car was on) and the car began to move backwards… My brakes were not working (because the car was 'off'), I then shifted the car to neutral as I was going backwards and then park - it is here where I heard a fast clicking sound and the car finally came to a stop. I drove around afterwards and everything was fine. By the way this is a 2012 honda civic LX automatic.

Read more: What affect could this have had on my automatic transmission?