A Killing at the Holocaust Museum:Questions Linger

A man named Mr. Amon Van Brun shot the guard, Mr. Stephen Tyrone Johns at the National Holocaust Museum, where he showed up sporting an armed rifle.Mr. Johns is now a ntional hero because it is thought that he protected the others in the museum at the ultimate cost.
Mr. Van Brun is a well known author of a white supremacist book about how the Jews in the world hurt gentiles worldwide.
The violence experienced here had many wondering why there are other people who want to suppress the evidence of genocide and racial hatred and deny that the holocaust even happened.
Why do you think this happened? Your thoughts please.