Don't get me wrong. There's a 99% chance that had I been in the same situation I would have done the same thing. You have protect you and yours first. It's why we all carry, isn't it? But then to come to find out the guy didn't have the mental capacity to understand what he was doing would definitely make me feel bad for having to take him out. In short, good shoot, bad outcome.
On the surface I agree wholly with this. But it wasn't clear where he got the toy gun from the article. I kind of wonder what his mental abilities were with him walking around alone in the first place. He may have been mostly functional but unable to handle situations where stress levels reached this kind of level. I guess if he shouldn't have been out in public alone the family will have to live with that as well.