A photo of Adolf Hitler loomed over the stage as a rock band called Definite Hate performed—a band that Sikh temple killer Wade Page was reportedly once a member of.
Page was said to be immersed in the "creepy world" of what's called hate music.
"The music is an indicator of potential violence," said Segal.
The ADL website says hate music is "one of the most significant ways neo-Nazis attempt to attract young people into their movement."
"Page is one person who was not only attracted to the messages of hate, but was actively involved in the movement and in the white power music scene," said Segal.
Page was also in a band called End Apathy, which has been linked to the white power movement and which pumped out lyrics like these: "Adapt to the trying times or pay with your life," and "Your life is insignificant."
The New York Post labels one of the shooter's groups a "looney tune band."
And hate bands have come in all ages.
Twin sisters Lynx and Lamb Gaede were famously in a white-power band called Prussian Blue.
Lynx and Lamb danced around a swastika on their kitchen floor, wore t-shirts with a Hitler smiley face, and gave the Nazi salute.
The sisters later renounced their white-power ways, something Page clearly never did.