All my years taking the subways in NYC left me unsurprised at how more folks did not get involved to help the soldier in Atlanta. I bet you have seen this also. Most folks pretend they do not notice lunatic behaviour in city subways and on the platforms. It shouldn't be that way though. It's the old Kitty Genovese syndrome (for those reading this who do not know about this classic psychological study: Genovese was killed in Kew Gardens, Queens decades ago after her scared neighborhood did not respond to her loud screams). We could stop some of the fear if we were all allowed to carry, IMO.
Quix is right in saying that the woman who stepped in was the only one who had the much-needed cajones. She and the soldier are heroes!
Actually, I see people step in to help more often than not.
You are quite right about the Kitty G syndrome.
Whenever there's real or perceived difusion of responsibility, the chances for help are greatly diminished.
I haven't heard or read of the following but were I in such a situation, I think [other than praying energetically in tongues] I'd scan those around and call out to the most likely responsible person by a clothing description or some such and ask for a specific action.
But given the raging sanctioned rebellion labeled individual freedoms; the hideous excuses for parenting yielding the dreadful lack of training in responsibility, I suppose it's a wonder the rest of the train car didn't join in, in the attack!
The heartless case I remember most was that of actress Theresa Saldana . The true story of the brutal attack on actress Theresa Saldana by an unbalanced fan . People watched, she begged, they did nothing!
http://us.imdb.com/title/tt0088349/