Edmonton fans were more than likely not pleased with the final score of the game in which their team got outplayed, and that situation presumably combined with alcohol is never a good scenario for anyone. Regardless of your personal opinions about the police, it's a good thing that the fight concluded before any innocent bystanders were hurt.
Fan fights seem to be on the rise this year and especially during the playoffs, fans should stick to watching hockey players go at it on the ice and not go at it on the street, to each their own though.