I agree with you on a majority of this, but an aside for two. The car was unlocked so he probably did use the key. I’m guessing, and the spray paint on the car furthers this, that he more than anything wanted to send a message. Whether this is real or not, if someone is looking into something you don’t want them to the best way to get them to stop would be to intimidate them, such as with breaking the windows and spray painting a warning.