It's not about rehabilitation, it's about removing him from society to spend his life proverbially rotting in the solitude of jail, it's about not justifying a death with another which is the very same reason that this stuff happens immensely disproportionally more in the USA. A place where life is worth less than anywhere else in the civilized world. A place where killing a guy because he wants to rob your wallet is justified. It's the same viscous circle that put the US in this situation. A place where fireworks are sometimes illegal yet a 26 inch barelled, 700 round per minute cannon of death is perfectly fine.