If we have no future, I don't see the reason why we should act as if we should. So let the boy murder a 7-11 clerk for some bubble gum, eh, since he's immune to the death penalty? As someone had said, there is not one moral Law for those who have years ahead of them and another moral Law for those who will pass into eternity tomorrow.
No he has no right to take others with him or to harm other people. (And I have no idea what neural circuits allow you to make an analogy between murder and consentual sex - I suspect it's mainly the fact that you can't think for yourself - and can only follow rules others make for you).