Here's the definition of terrorism (not US law, but I'm guessing it's similar):

terrorism, the calculated use of violence to create a general climate of fear in a population and thereby to bring about a particular political objective.

This doesn't appear to match that definition, this just seems to target one neighbor, so it's a hate crime.

I don't see any political ends here, nor do I see a broad climate of fear. It could be terrorism if they were part of a larger group that did this all at the same time, but I see no evidence of that.