This guy is a bit like you and me, and everyone else.
A guy in his 60s who got mad at people — you don’t see that very often. /s
I wonder if the search for political context will be an essentially bogus waste of time and we are left with either (a) the guy suffered from an undiagnosed medical condition that affected his cognition, or (b) he was pressured into participating in this or even just kidnapped and dumped into the scene when the actual shooters were done.
They would, of course, target a person who had shown some interest in guns (hence the reports from St George UT of several visits but just to buy regular guns).