These people heard of the riots FIRST, the cop killing was not major international news until the riots. So they are following what they saw on tv and social media, that the world is rioting and protesting, so they do to. We have become a world of puppets, that follow what they are told by the media. It's scary.
I was a kid in the 80's and very few people had tattoos. They knew of them, they were around for 1000's of years, but no one wanted them until everyone had them, now every 16 year old girl gets her butterfly tattoo on her 16th birthday. While a trivial example, people just do what they are told everyone else is doing, from tattoos, to black lives, to Socialism. There is no more independent thought. The world has become one big advertisement, where you don't think you are watching it, it's boring and you "think" you are just hitting "skip ad" or going to the bathroom during a commercial, but it's getting in your mind. Your decisions are no longer your own. That's why all the pop ups, the tracking, the "guided searches" from Google. Our real, sensory experience has been replaced with what we are told what is happening in the world by digital screens.