This is real live hooliganism between fans of Valencia and FC Bayern Munich in downtown Milan.
It really does amaze me how pointless violence is practically a hobby in some parts of the world. I read a book about English hooliganism written by a gonzo journalist who traveled with the hooligans themselves. You know, they plan for the violence. It doesn't just break out spontaneously. They travel to remote locations with the expectation that they will crack skulls and that their own skulls will get cracked.
It's truly an intoxicating, addictive feeling for them. And a practice they continue even as their friends are seriously injured, imprisoned on foreign soil, or killed. If they actually see the game associated with the trip, that's very secondary to the whole experience.
We Americans think we have a violent culture. We have no idea.