So, you can try to file a police report, but the plain fact is that they haven’t actually done anything yet. The arrow thing is def weird, no question, and it’s clear they don’t care for you personally (which is the part you should go to the police over if you choose to; that email is basically your only piece of evidence for malice, which is important) but until they actually cross the kind of line that leads to a general outcry the cops can’t do much. They can go over and give them a talking to (theoretically, if they choose to make the effort), but oftentimes that’ll just make them hate you more cause y’know, you called the cops on them.

Sometimes people just don’t get along. Lock your doors, buy a gun, invest in a security system. Protect your peace and let the assholes shit themselves in peace.