Why all the sirens yesterday?

I heard an unusual number of sirens in my neighborhood last evening. I associated the noticeably higher incidence with what I assumed were the post-game hours. Here in the Bay Area there were undoubtedly a lot of disappointed fans.

My question: what goes on after a game such as the Superbowl that requires so much attention from police and other emergency services? What are people doing to themselves and each other?