I'd say, you can't just kill someone for no other reason than to have their organs, however, if it was for five close loved ones, and you volunteered without being asking, then as an extreme, I'd say it might be okay for Bill to be killed. I'd say it depended on who the hostages were. If they were loved ones, or innocents, then I would fight for them whilst being willing to die. If it was the case that it would be impossible for me to die, then I would use every nanosecond to weigh up and down who I would save and why. I would choose one person to die if it meant saving others. In the case of saving five people from a tram, I would ordinarily go for the one to save the five, 'however' if the one was my Son, I would kill the five. Goodnight Bill.