Hypothetical - Sacrificing yourself to save others

[hoyasnaxa]

Here is the situation; lets say you are in class or at work or whatever, and a bunch of gunmen walk into the class and inform you that they will kill one person in the room at random, unless someone steps up and volunteers themselves. Would you sacrifice yourself to save others? Assume that there is no way to avoid someone being killed.

Would the number of people in the class affect your decision, like a class of 10 compared to a class of 300? What if your wife, girlfriend, mother, one person you care about a lot is in the group, would you step up in that case? Just wondering.