i don't think with a gun you can find a 100% clean solution, but shooting him will be better for society as a whole.
John:
As a Christian (and I mean no disrespect to any non-Christian, as there are many here who I have befriended in the past year or so I've been a THR member), I have to disagree. I know Christian sects and beliefs vary, but they way I was taught; it is not the right of any man to decide the fate of an evil person in contrast to the whole community. That is for The Lord to decide.
What we ARE taught though, is to take care of our own, and to protect them when they are in immediate danger. To put this in layman's terms: If I see someone being robbed at gunpoint, the Bad Guy is getting "one to the dome", No Questions Asked. However, if the robbery has just occured, the victim is no longer in immediate danger, and the perpetrator has fled; then I'm going to get as much information about him as possible, notify the police of this information and his whereabouts, and allow them to arrest him and bring him before justice, among a jury of his peers (the community). It will be at that point, by the community (jury), for the community, to decide that man's fate.
Either way, speaking from a Christian standpoint, he'll eventually have to answer to The Man Upstairs.
I know I've repeated some of what others here have already told you. I hope I've answered some of your questions regarding the religous and social aspects of your original inquiry.
As for "why the law is", maybe I have answered that; maybe not. Do consider though: A lot of laws have been written looking to the Holy Bible for guidance.
Take care and stay safe.
-38SnubFan
P.S.: I'm not accusing you of being a troll, for no one really knows if you are one. I will say this: If you are "trolling", you're not going to get the "Yeah! Shoot him!" response from ANYONE in this forum. And we won't be keeping this going for your amusement, but for our own. If you continue to be amused (again, this is IF you're trolling, NOT an accusation), that's at your own discretion.