Everybody's heard of the My Lai massacre - March 16, 1968, 50 years ago today - but not many know about the man who stopped it: Hugh Thompson, an Army helicopter pilot. When he arrived, American soldiers had already killed 504 Vietnamese civilians. They were going to kill more, but they didn't - because of what Thompson did. We started noticing these large numbers of bodies everywhere," [Thompson said]. "They were old women, old men, children, kids, babies." Then Thompson ... "saw some civilians hiding in a bunker, cowering. Saw some advancing Americans coming that way. I just figured it was time to do something, to not let these people get killed. Landed the aircraft in between the Americans and the Vietnamese, told my crew chief and gunner to cover me, got out of the aircraft, went over to the American side." What happened next was one of the most remarkable events of the entire war, and perhaps unique: Thompson told the American troops that, if they opened fire on the Vietnamese civilians in the bunker, he and his crew would open fire on them. "I thank God to this day that everybody did stay cool and nobody opened up. It was time to stop it. That was the only way the madness ... could be stopped." Back at their base he filed a complaint about the killing of civilians that he had witnessed. The Army covered it up. But eventually the journalist Seymour Hersh found out about the massacre, and his report made it worldwide news and a turning point in the war.