Last week, 10 foreign aid workers, including 6 Americans, were killed in an ambush in a remote part of Afghanistan. The U.S. victims, who worked with the International Assistance Mission, spent years helping the world’s most impoverished. The Taliban claimed responsibility for the slayings, claiming that the victims were spying for American forces and proselytizing, which is illegal under Afghan law. There are roughly 1,600 NGOs currently operating in Afghanistan alone, staffed by thousands of volunteers. Why do people do this kind of risky work? How do charity organizations cope with this kind of loss?