It turns out I saw the guy walking around our neighborhood over the last couple weeks. Both times, I was creeped out, there was this slightly disheveled guy walking down the street (right in front of the high school) scowling and having a loud angry argument with ... nobody. At first time I thought maybe he was on a cell phone, but by the second time I was pretty sure he was talking to himself. He looked like he could certainly boil over, it is definitely not normal to have someone walking around in a rage for weeks. I can't really buy his family and friends saying they didn't think he could ever be violent, given his outward demeanor on the street. He was putting out danger signals that got the hair on back of my arms up.
I do have to agree that whatever mental health system we've got is not working right, if his family could not get him locked up as they had reportedly tried to do.