Chicago Cops have been known to start a riot or two. In 1968 they even brought in the National Guard to help them.
Yeah, I still remember those (watching the riots on TV, of course.) I was 13 at the time, and a confirmed "law-and-order conservative" who was convinced that those "dirty hippies got what they deserved" (to quote my policeman father.) These days I realize that is not true at all.
At least in the Chicago riots, most of the people who were injured by the police had actually gone out to protest or even
seeking a confrontation. but it doesn't seem as though that was the case in Pittsburgh. It's my understanding that most of the people harrassed and injured by the police were innocent bystanders who weren't even involved in any protests.