Vandalism

We had a little vandalism at work over night.  When we got to work this morning, we discovered that the window had been shot out.  There was glass everywhere.  Apparently this was not the first incident.  Last week there was a vehicle window that had been broken as well.  I just don't understand what is behind these kinds of acts.  I understand anger and frustration, but destroying property makes no sense to me.  Guess I better keep reading my social psychology book.  Maybe that will help me understand.