I think it is easy to determine where violent action is taking place, fly the helicopter a few feet over the buildings and notify people deadly force will be used in this area, and then start shooting. If you want to be squishy, you could start live fire with rubber bullets.
Then again, I've been where police started shooting pepper balls and rubber bullets without any warning; I was standing three feet away from the cameraman who took a shot to his camera lens covering the DNC freakshow in Los Angeles in 2000.
Back in the '60s, when the Italian Communists used to riot in the streets on a weekly basis, the police loaded their water cannon with dye, sprayed the rioters and then afterward, arrested anyone so marked.
In the current situation, use a brilliant yellow and do the same. The side benefit is that the rioters would make excellent targets illuminated in this manner.