I agree with the advice that maybe the police need to be told. This guy needs help and support. He must be going through hell in his mind in order to do what he is doing.
As for whether he is giving apostates a bad name. I can see your point of view. But for every fanatical apostate, there are, I'm sure, probably at least double the number of fanatical JWs. Maybe not resorting to such drastic measures, but enough to put normal people off JWs. I can think of several I have known over the years (you know, the type that take witnessing to the extreme, not respecting personal boundaries or body language that shows someone is REALLY not interested). Yes I think on balance, this guy's actions are not going to make much of a net effect except, as you say, give the local JWs a few war stories that will probably turn into urban legends. Still, let them have their fun. In the meantime this poor man needs help.