Don't be too quick to point the finger. Witness statements and security camera footage has already shown what are dubbed "professional rioters" coming out of alleyways prior to the ruckus wearing balaclavas and sporting weapons, molatov's, tire irons, etc... likely the same type of people that showed up in Toronto for the G20 summit and started problems there. Riots are like a contagious disease, people who wouldn't think of starting one become susceptible to being swept up into the riot mentality and joining in once it starts. For example...you're standing there minding your own business, people in your immediate vicinity start flipping a car so you stick around to watch, the cops show up in riot gear and slam into you with a riot shield because you're in the area and piss you off. Bingo, you're now a rioter. Also, don't be fooled by the targeted media coverage, out of the tens of thousands of people out on the streets that night very few of those people were actively burning cars, breaking windows and wreaking havoc. I'm sure a riot could break out amongst post-fight MMA fans who've been drinking just as easily as a group of hockey fans given the right instigators.