I remember feeling that the whole story never came out, I think the widow has info she is not giving up, normal well balanced people don’t just wake up and do things like this.
What info?
Maybe he was a little more quiet or short tempered than usual. Maybe he was paranoid about some things. Maybe he was acting just a little bit odd and not like himself..
Surely you don’t thing that she would have been able from whatever changes in his character to think “A HA! He’s going to go to a school and kill a bunch of kids!”
Sorry, but even when someone gives clues about going ‘off’ they’re only clues in hindsite.
Does his failure as a husband, father and as a man indicate that somehow his family (wife and children) were responsible for it? I think not. It's called personal responsibility!
What info?