The man who shot and killed 10 people in Buffalo, NY, seemed to believe based off his writing in the 'great replacement,' a fringe belief commonly perpetuated on Fox News. Here's what you should know about the racist, far-right theory. (warning: distressing themes)br » Sign up for our newsletter KnowThis to get the biggest stories of the day delivered straight to your inbox: » Subscribe to NowThis: br For more U.S. news, subscribe to NowThis News.