The problem is.. chances are, the incident took place on private property. This means, unless there was bodily harm, or a preponderous amount of damage, or a cop actually witnessed the event then you are SOL. In private property, different rules take place then on the public roadways. Keying a car is considered a MISDEMEANOR in most states. I'm serious. Look up the laws as I told you, but even if you WITNESS the guy doing it, and even caught it on film, all the guy has to say is that it wasn't him. Now your footage is not immicable(sp?) in court. Sorry a bit woozy to spell correctly so please forgive me.
I'd like to help you out, but if that ever happened again and you witnessed it... beat the FVCK out of them. I'm serious. Claim self defense and you'll win. I've done it before. Not a mark on my record. You just have to say you were IN the vehicle when it was damaged and that he was threatening you bodily harm as well as property damage. Bingo.. now you have free right to act in ALL 50 states to defend yourself.. if need be to the death. I don't recommend you try the death part thought.. just saying it's been done and successfully tried before. It's an unalienable law and right to self and property. BUT it has to be to self AND property.