So I wasn't down there but had a lot of friends who were. They said that they saw people with ski masks and bottles of gasoline BEFORE the game ended. A bunch of people went down there just so they could riot, win or lose.
And it is likely people from the suburbs who did this. There are plenty of stories of people leaving their apartments to run into the street and defend businesses.
Would you be allowed to defend your home or business with force if needed? Like could a shop owner guard his store with a shotgun? Obviously he can't stand out on the street and shoot people who threaten him. But if he is inside can he protect his property if people break in and threaten him?