This reminds me of another cop vs. crowd incident in Chicago from my younger days, one with far less sinister undertones.
Several decades ago in Chicago, at my undergrad university one winter after/during a snowstorm, a snowball fight broke out between the frats . . . and a lot of non-frat students joined in.
It spilled across State Street, which drew the ire of one of Chicago's Finest, who decided it was up to him to disperse the crowd and stop things from getting out of hand.
It was FAR too late for that, when a cry arose - GET THE COP!
Under a hail of snowballs, the cop retreated to his car, only to find . . . it was now filled with snow.
Other units arrived and the group of snowballers dispersed with incredible speed, disappearing into the crowd of very sedate and well-behaved students on their way to and from classes.