From what I've read the guys wife died recently and those neighbors were taunting him about it and making fun of it.

I know for a fact there's at least a couple people that I love so much that if they passed away and someone bullied me, told me that they're happy my loved ones died. Told me they're burning in hell, that they were worthless and its good that they're dead FOR MONTHS I would be pushed too a pretty dark head space. Its possible you don't have anyone in your life that is that close to you so you may not be able to understand how someone can get pushed off that edge but a lot of people, while they themselves wouldn't shoot anyone, can at least understand how that treatment can push someone over the edge.