The "spark" will be generously-provided by those on the left, who would like nothing more than to create a divisive atmosphere, to gin up hatred between different classes of people based on racial, political, economic, and ethnic differences among the people. Thus has always been the primary tool which cultural Marxists have used to carry out their quest for "change."
Of course, one could also throw in the classic "victimhood" the left employs as one of their primary tactics. By instigating unrest which ultimately results in violence, the left absolves themselves of any moral responsibility, and graciously gives them the opportunity to claim that we fired the first shot, thereby giving them the full authority to respond by whatever means they deem necessary.
For a historical perspective, look up the "Reichstag Fire", that Hitler used to gain control. It's all about control, you know. He was more of a leftist than history would lead us to believe. In fact, both Hitler, Stalin, and Marx are probably sharing the same fiery cell in Hell right now.