Everyone has their little points they hate - whether it's 'long haired punk kids' (never mind the behavior, the long hair is the crime), or poor grammar in posting online or just the pitch of someone's voice.
Anyone willing to kill over that is more dangerous than thieves who kill at least for predictable reasons - this person is willing to kill over trifles! Unpredictable and anyone could trigger it - that neighbor who mowed a foot over the line is sure lucky the guy wasn't having a bad day that day! All he did was yell at them a lot.
"Straw that broke the camel's back", etc. - maybe, but was it reasonable at all, in any way, for that straw to be it? This guy had a choice, and he chose to get his gun, and wait for the kid to show up. He wasn't physically broken (like the camel's back) - he made a choice. The weight on his mental camel's back was minimal and nothing anyone else would have killed over - that's the problem. Gang leaders think killing over a bit of disrespect is OK, that that last time the guy walked through his neighborhood without paying respect was their straw that broke the camels back. Abusive husbands think finding a kleenex on the ground is the straw that broke the camels back in justifying a beating. The question is - was this reasonable - not what he thought inside his warped mind.
Just because some people think it's reasonable to kill or maim over these trifles doesn't give me any sympathy nor understanding towards them - it gives me less to know they really honestly believe they were justified, entitled to that respect, to that level of control over others.