Riots

Any excuse to riot and some people will go out and do so.

Sometimes enough people will be out to protest something, to get people to act more bold and act up, and while the police are busy others will take advantage of the situation and begin breaking into stores and stealing things. Some will destroy property, start fires, just for their own enjoyment, without anything to gain from it.

Even without protest, some conflict has happened when an emergency situation happens, and people get into violent conflicts over the last toilet paper the store has to sell, etc.