Earlier quoted context omitted.
If the web page linked in another comment is authentic, the attacker was in a very bad mental state. I don’t think we can completely rule out previous contact, and the attacker was unhappy with his team members, but random chance also seems possible. I lean towards authentic because a) the journal document is much too long to have been produced quickly, b) the text isn’t lifted from other sources, and c) the website…
Making Holocaust video games isn't exactly non-extremist.
And it wasn’t important enough for him to list on the standalone games pages.
Now, Prophet Shooter is unambiguously anti-religious, so maybe there’s something there? And he’s got a Trump parody game. I’m not 100% sure here, just leaning against it. It’s also certainly true that sometimes extremism is the result of mental illness looking for some kind of framework to cling to.