My son was at a friends house the cars were parked in the driveway. The person that lives there and his buddie backed his car around my sons car and when the buddie got out he left the door open and went to wright on my sons windshield with car chalk. My son tried to back up (He was trying to leave any way) to get away from him so he wouldn't have to clean it off. He hit the other cars open door. Who is at fault?