sjw,

If you're talking about why the guy went wacko, I'm not sure an underlying story will ever be found / told. You're right, our animal brains sometimes get a hold of us. Some people do snap. As I said earlier, I can't understand the hate / rage that drives people to do this kinda thing, but that's just me. Circumstances could probably turn most people into hateful animals if they let them. The trick is not to; and ... sigh ... not everybody gets it.

(sorry, enough philosophy for the day)