Thing is, it's not just "a video from one guy". I was watching CBC, and they were showing crowds with enough camera flashes going off that I think if one of the rioters was epileptic, he would have gone into seizures by just looking over his shoulder. Many dozens of cameras and phones lifted up to catch what was going on. Someone higher up mentioned photoshopping in someone you don't like, which wouldn't work because of the twenty or thirty other pictures of the same scene without that person there. And other people have mentioned that the police are asking for their help. To address your initial point, the vandalism, and even assaults that resulted in the most minor of injuries, are all crimes. It's their job to try to catch, and prosecute, the perpetrators, whether or not it's a pain in the ass to do. Even arresting one person with evidence from multiple sources would be a win, as far as I'm concerned.