Yikes. Saw this on the news this morning. In Argentina there was a riot that left 20 people injured (they set fire to the train!) The train was already 50 minutes late and they'd just been told it would not be leaving at all due to technical problems.
The passengers then joined "masked demonstrators" in throwing rocks at the train and generally all hell broke loose.
Masked demonstrators? It's believed that the entire thing was actually orchestrated by "members of the railway unions and leftist groups."