I was parked at a gas station today in a parking stall. I looked around and no one was coming so I proceeded to back up. I stopped to double check no one was coming as I backed up and a car that was in line for gas started backing up towards me.

I honked my horn and the other car stopped backing up. (I still was not moving at this point). Then the car backed up even more and hit the back of my car.

My car did not have any damage but their bumper was smashed a bit.

My question is.. was it 100% their fault or will it be 50-50?

I realize that parking lot situations are usually 50-50 but since I wasn't moving when it occured I thought it might be all their fault. Anyone know?