So, if you torture and killing X children because X + N people are at risk, just how are you different than the person who has put X + N at risk? At at what point is X large enough to suggest that you do not torture and kill? What if you needed to torture and then kill X + (N-1-x) in order to save N? Just how many are you willing to torture and kill in order to save another group? Who choses which group is more "worthwhile" to save?