Murder mode is a stupid addition. That said, you can blame the games shoddy architecture for its existence. As far as I understand, dayz basically stores bullets in a table somewhere, shouldn't be too hard to find the offsets, last patch it was 0x4 in the WorldJ + something table.
Then it's just a matter of digging up head locations for entity, finding the vector for the bullet, then using magical teleportation powers. It's very easily detected, and most will be banned within hours.
EDIT* What I mean to say is, please don't ever add murder mode, and for people reading, please don't ask him for it. There comes a point where hacking bring diminishing fun returns.