“Turning the other cheek is for when you yourself are oppressed. I’m not the person raped in a detention camp. I’m not the fisherman executed without trial,” it said. “I’m not a schoolkid blown up, or a child starved, or a teenage girl abused by the many criminals in this administration. Turning the other cheek when someone else is oppressed is not Christian behavior; it is complicity in the oppressor’s crimes."
“I am no longer willing to permit a pedophile, rapist, and traitor to coat my hands with his crimes."
"In order to minimise casualties, I will also be using buckshot rather than slugs (less penetration through walls). I would still go through most everyone here to get to the targets if it were absolutely necessary (on the basis that most people chose to attend a speech by a pedophile, rapist, and traitor, and are thus complicit) but I really hope it doesn't come to that."
Those are the bits of the "manifesto" that I've seen quoted in the press.
It reads as genuine sentiment, to me.
I think the instinct not to trust a thing that comes out of the Trump administration is a sound one. If they have no credibility, they have only themselves to blame. Nonetheless, the simple explanation is usually the best, and I don't see any compelling reason to buy into "false flag" theories, here.