Problem with that is when they pay their 100 dollar ticket then they come after you harder. Nice to come home and find your house vandalised or your dog dead. I say shoot them. I have learned my lesson with formal complaints to the police.
Once they've been cited and paid up you should initiate a civil suit for property damage. The citation and fine is pretty strong evidence of guilt in a civil suit because they've basically admitted guilt or been found guilty in criminal court which has a higher standard of evidence than civil court.
So your friend needs to document the evidence of the damage the costs of fixing the damage, and every other harm you can imagine up. Go after the one with the deepest pockets and get a fat judgement against him.
As for the thug/terror tactics that is a tough one if you can't get LE to stop turning a blind eye to it. PITA, but you may have to install a tone of security cameras to gather
evidence they can't ignore.
Unfortunately fighting a legal battle against people who don't respect the law and seem to be getting a pass from LE and the rest of society at large is expensive and requires a lot of determination.
I fear the U.S. is devolving into third world conflict resolution of bribery, kickbacks and corruption faster than I expected.