I think what I am trying to say is that the punishment doesn't make some people reconsider when they're about to kill someone. Discipline needs to be harsh in order to have someone contemplate what they'll do.
We used to have thieves hands cut off, did it detter everyone from stealing, did stealing become more common when that punishment was removed? No, it didn't. The reasons why people commit crimes are many and range from fanatic zealotry to desperate poverty. Beating your kids is one way to raise a kid, but that kid might just aswel decide that becouse you beat him, he has to be less open about who he is, or what he does. He might become more desperate when you find him out. As stated before, a criminal who realizes he is gonna get death penalty, will likely try to go out in a blaze instead.
Also, I was the target of three men beating me to the inch of my life, one of my friends were killed by hooligans in supporter fight between local teams here and I lost a uncle to malpractice. In neither case do I think death should be the penalty. It would not bring me my two preciuos friends back, one wich was family nor undo the abuse that I was forced to undergo. The ability to lament and Rehabilition are two things we as humans take for granted all to often. We are so blinded by our shortsighted need for immediete satisfaction that we do not understand the implications of our actions.
Do the kid deserve a harsh punishment? Yes, he does. He needs to live with what he has done, locked away till he is no longer a threat.