Don't take this the wrong way....just a thought.
Maybe the person/s that did it seen how protective you were you your car and seized the opportunity to get you where it most hurts. I dunno, but it looks like someone has a grudge against you for some reason. I'd guess that the vandalist/s are definately from your neighbourhood. I don't know how you go about getting revenge. It's a tough one mate. Maybe try baiting them, but i'd doubt whether they would come back. And i would also say that there would have been more than one person involved.
Regards,
Scott.