Nil Köksal speaks with director Kim Nguyen about his new documentary "Saigon Story: Two Shootings in the Forest Kingdom." In it, he pulls back the curtain on one of the most famous images from the Vietnam War: Saigon Execution. The film explores how the act of violence captured in that picture, and its aftermath, have rippled through generations, and tells the stories of those who've had to live with its impact.