Yikes.. what a scene. I'm glad for the outcome; a bunch of people helped make it happen, american buddies on vacation, an englishman who lives in France who used his tie, a French actor, and I think a second french guy too.
account here:
http://www.theguardian.com/world/2015/aug/22/us-student-tells-of-attack-on-french-train-gunman
Sorry if there is already a thread on this - I didn't see one on a quick look.