Here's an instance of another train invasion where a passenger did fight back:
http://www.myrepublica.com/portal/in...&news_id=27100
To sum up, a Gurkha soldier armed with a kukri knife fought back against a gang of about 40 robbers invading a passenger train, killing 3 and wounding 8 before the rest fled. I think the story justifies the more levelheaded comments here:
1) He did not draw his weapon until passengers were threatened with serious physical harm. In the MARTA case passengers were beaten, but the article does not make it clear whether or not lives were in danger. It is impossible to tell without actually having been there.
2) Once the fight started, the robbers did NOT back down at the sight of a weapon. They kept fighting for 20 minutes even after some of their own were killed. It's dangerous and arrogant to assume that 'just because they're criminals, they must be cowards'. A defender on the MARTA car may have faced a similar situation at least until the train reached the next stop.
3) The soldier did not even have a gun, but once he made the decision to fight he had a win-or-die mindset. There's been a lot of talk in this thread about capacity and ammo performance, but it seems those things are unimportant next to the mindset: if you have to fight, don't stop until you win.
4) A kukri cannot cause innocent casualties by way of missed shots or ricochet, so the soldier did not have to worry about something that a CCW on the MARTA would DEFINITELY have had to take into consideration. I personally would rather take a beating and lose my wallet than accidentally kill a bystander, or cause one to be killed through my actions.