He appears to be from a good family - but became self radicalized as an online leftist/ anti fascist. The bullet casings have numerous antifa slogans and song names. One of the casings had inscribed on it "Hey, fascist! Catch!" Well, mission accomplished. Charlie (whom Robinson believed to be a fascist and a "spreader of hate") caught the bullet. The online left (not here) now rejoices.
The issue is that the online left believe that "words are violence" and he expressed to a relative that Kirk was a spreader of hate. Thus, he (in his twisted mind) felt it reasonable to respond to Kirk's violence with violence of his own. Where did he get the idea that Kirk was a fascist? From virtually every Dem politician, media person, online writer and podcaster and strongly implied by the last President. Disagree with us all you want. Fight back against Trump's overuse of the Executive Orders, but quit constantly labeling MAGA fascists and Nazis or YOU are going to inspire future Robinsons to kill other conservative public figures. I mean if your democracy is a stake, isn't murder of MAGA justified?