Posted this elsewhere but will join into the discussion under this meme as well:

So, this is 100% speculative rambling at this point, but as a gut feeling on my part that can be proven wrong: I get the feeling it might have been someone from a Republican family, possibly shitty family psychology-wise, registered as Republican for his families sake but got f’d up by the pressure within his personal relationships and the state of the world, who radicalised himself on the internet.