It's never been a secret that White Nationalists aka the KKK and Nazi groups in this country endorsed and backed Trump 100%.  They were even making robo calls for him during the election season. Trump was also encouraging violence at his rallies.  I am not real surprised to see this kind of violence.  They have been emboldened with whom they consider to be a "friend" in the Oval office.  The Republican party has added a new wing called the ALT right--which I am certain they're not happy to have join them. But they're here now because of Trump.  

This is what Hillary Clinton meant when she stated that half of the Trump support group are "deplorables." We all saw and knew this, it was just ignored, like everything else about Trump has been. It's a sad day for America to see this kind of hate in this country.  
https://www.washingtonpost.com/news/post-politics/wp/2016/01/12/why-this-leading-white-nationalist-is-urging-iowa-voters-to-back-donald-trump/?utm_term=.b4ab5ddf854f