So we all know that Jacob can not be killed by otherman or vice versa. So this is the reason UnLocke gets ben to kill Jacob. Remember that when ben stabs Jacob he was still alive, dieing...sure but dead he was not.... then jacob mudders the clif hanging words they're coming and is kicked into the fire by unlock/otherman. Since the fire would have killed him first insdead of bleeding to death otherman/unlock would have been the killer and since we all know that is against the "rules" Jacob is far from dead.