They’ve happened before and the will happen again. The reasons the next one(s) start may be different, but there will be some common elements. Local criminals first, then criminals, anarchists, and professional agitators from outside the region will start looting, burning, beating, and maybe killing (depending on how long it goes and how big it gets).
Motives are irrelevant to the subject of this particular study of riots. What is relevant is what happens and on what timeline things happen. And what you can do to avoid it or to escape it or, in extremis, to deal with it.
If something happens in your Area Of Operations or Area Of Responsibility (AOO where you are; AOR where somebody you care about is) that could trigger unrest or starts a public protest, keep an eye on it and keep an ear on it. That would also be a good time to check any riot-specific plans and preparations you have and do what is necessary to plug what holes you can in the near-term.
Consider the addition of things such as smoke generators (i.e., grenades) and things like OC foggers and (if you can find them) CS/OC grenades to your vehicle and some other places you are or have to be at regularly.
Check the street maps again. Get some routes in memory. Don’t count on being able to look at a GPS while you’re jinxing through a possible conflict zone.
Set the vehicle up as best you can to be able to go through or around obstacles (animate and not) even if it means leaving the street to do it. And study proper ramming technique, while you’re at it.
Consider the addition of a car or truck gun to back up your carry weapon.
Those of us who work or operate in areas that restrict carry and storage of firearms should think seriously about what circumstances and under what conditions we will break those rules in order to have weapons at or near to hand. This is a more serious consideration for some than for others. Better, then, to make what decisions you can about it, set what lines should be crossed, and as best you can work out the limits to your willingness to obey those rules in the face of potential group/large-scale violence in your area.
There’s other things, but these are some things to think about while you have time and space.