The only fitting punishment is one that can't be applied from the outside: if he were to lie awake every night for the remainder of his natural born days, wake up sweating, seeing the faces of the two people he killed staring at him everywhere, accusing him, haunting him. Standing like shades behind all his family at any celebration, there every time he looks up, every time he says good bye to a loved one in the morning and has to wonder, will they come back safe or will they be unlucky and meet a man like he is himself.
Even so, it wouldn't help bring back the dead.