An Ethnocidal-Religiocidal 21-Year-Old & Nine Innocents: Why?

I am trying to understand how a man who's my age could be so hard-hearted and evil. What was his motive? Infamy? "Revenge" for the racism in this country of late--how does racist violence against innocents rectify any wrongs? Evil for evil?--maybe he had a grudge and racistly scapegoated? Trying to be cool and impress his fellow ex cons? Racism and crime are never cool. Suicide by cop and murder? Why didn't he take just himself in any case? Either way, he needs the death penalty--preferably by firing squad.