By the time you get to incidents like police's violent arrest of SNL's Jay Pharoah [0], complete with knee on the neck (fortunately not long enough to kill him), you have potentially hundreds of thousands of people being affected and treated like this every year.
Murder rates have gone down since 70's and at their lowest point, but with the introduction of national and world news it makes people think murders have gone up, so they don't let their kids walk to school. Some people have an irrational fear of flying because of news. People have fear of skydiving because they watch too many movies and think a parachute will fail, when the data shows the exact opposite. 99% of are deaths not related to parachute failing.
So I see the police killings as a world that has gotten smaller, video camera's in everyones pocket and social media that has painted a picture of world that doesn't exist. It strikes fear into people and the psychological issues will be felt for decades.