The only response I feel is appropriate to this thread would be to address 2 issues.
1. Was he within his rights to defend himself with lethal force? Yes (probably). It's hard to say from a simple news article. No one knows what really happened (except the boy, at this point), and 9 times out of 10 the media prematurely picks a side and shoves it in your face regardless of the evidence.
2. Was he morally in the clear to cleave the guys hand off and gouge his chest out with a razor sharp sword? Highly unlikely. In my personal opinion, if you don't have the discipline and skill to use a weapon in a humane way, you shouldn't have any business wielding it.
And no, I'm not being biased. I'd have said the same thing if he shot the guy 27 times or repeatedly bashed his head in with a baseball bat. Makes no difference. If you can't incapacitate someone humanely, use another (more immediately deadly) weapon. Guns people. Use guns. Swords are obsolete. Just 'cause you can kill someone with a sword doesn't make it any less harsh.
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Mind you, I'm not commenting on guilt or innocence here; I'm not saying the burglar's life wasn't forfeit, nor am I assuming the boy had a choice at the time he was attacked. If his story is true, I would never prosecute him. I would definitely order him to take a psychiatric review though. Violently killing someone would have a marked effect on anyone's psyche. If it didn't, there are definitely some more disturbing issues afoot.
What I'm really saying is that 1 bullet could have quickly solved the problem without causing unreasonable trauma to the assaulter. Hell, it would have probably been a much better deterrent than the sword.
P.S., No, I don't give a care about the NRA, before anyone goes assuming I'm some gun nut. Lol.