Recently witnessed something similar. Guy in his 40's/50's was reversing and smacked into a Commodore pretty bad, and left the scene.
As I was writing the note, the lady who owned the car came, so I just spoke to her, gave her my details, as well as the rego of the offending car, and heard from her insurance company as well as the police to make a statement the next couple of days.
I'd just hate for it to happen to either of my cars, so I'll help out where I can.