Sorry Sparrow dow, I meant to hit the like button, love the picture.
I think it hasn't happened for a few reasons. Many JWs that are disfellowshipped or treated unfairly are still believers and have some fear of Jehovah, so that probably keeps them for doing anything like that. Also, the governing body mostly stays in New York, and it's not that easy to get there for most people, and if you did how would you get to them? I doubt they let anybody off the streets into see them. Another reason could be that the JWs are not that big of a group, so the chances of having someone that deranged is probably not that great. There are just not that many truly deranged people, like the Aurora Colorao shooter, in the whole country. That one still creeps me out, I lived in Aurora and went to that same theater many times.
Still, it could happen, it just takes one. I hope not though, as much as I hate the GB