Boerum Hill #1: Weird Chalk Marks on Trees

What is going on in Boerum Hill? We'll deal with the subject of attacks on cars in moment, and direct you to the continuation of our Mad Crapper story if you wish to be enlightened about that. No, this is about something else:

Here's a weird thing. My wife and I noticed unintelligible chalk marks on a tree a couple of weeks back; the next day, the window of the car parked next to it was smashed. A couple of days later, similar chalk marks appeared on the tree in front of our house, and that night, our front house window was smashed. Today, chalk marks appeared on a tree in front of a neighbor's house; we hosed them off. I remember a story a while ago from the proprietor of 'home and abroad', who saw some kind of marks on her store window shortly before it was robbed. Anyone else noticed these? Is the Blair Witch vacationing in BH?

What's up with that?