A Father's Agonizing Choice

You are an inmate in a concentration camp. A sadistic guard is about to hang your son who tried to escape and wants you to pull the chair from underneath him. He says that if you don't he will not only kill your son but some other innocent inmate as well. You don't have any doubt that he means what he says. What should you do?

This is an easy decision. Although I do have sympathy for the other inmates, I would rather not kill my own son. I wouldn't be able to take the depression after being ordered to kill my own son and then killing him.