[Z]

This one is hard to decide upon. As you said, the guard seems like someone who kills people for the fun of it, I don't think I'd believe him if he said that me killing my son would save him killing someone else.. I mean, he's a guard at a concentration camp, he kills people for no reason all the time. And I certainly couldn't live with the guilt of being the one to kill my son. In this case, although I like to try and save as many lives as possible in these scenarios, the cause of death is unpredictable and untrustworthy so I think I'd choose to not take the chair away.