NPR's Ari Shapiro talks with Sophie Bjork-James, a post-doctoral fellow at Vanderbilt University who has been following white supremacist groups online for nearly a decade. They discuss the origins of Trump's tweet, a GIF of Trump pummeling CNN. Someone by a vulgar username posted what is believed to be the original GIF on Reddit, five days ago. The user has a history of writing hatefully about African-Americans, women and Muslims.