I suspect this doofus is just the patsy. I'm using that term loosely because the crime can never be pinned on him and isn't supposed to be. He didn't do it and could never be convicted. We're all just supposed to argue about him until everyone loses interest in the whole incident. Reference the previous Trump assassination attempts.

I would hazard a guess at the following scenario:

This dummy does all the suspicious shit like posting the song and walking around in front of the cameras and whatever else. For all the surveillance video, there's not one second with him carrying a rifle. That's because he never had one.

The real assassin had an accomplice at the venue, probably someone planted earlier on the maintenance staff. He brought in the real murder weapon and stashed it for the assassin. He also had to let the assassin up on the roof, since access is typically alarmed or simply locked.

The assassin retrieves the rifle, shoots Kirk, and hands it back or drops it in a stash location. Then he blends in with the chaotic, alarmed and confused crowd and eventually slips away.

The accomplice can get rid of the rifle any time. No one is looking for it anyway because the cops already found "the murder weapon" in the woods. It was planted there who knows when with all its bullshit iconography, which the scriptwriters somehow think is convincing. More dumb shit to argue about. This is why no one was seen carrying a rifle around that day: no one did.

Maybe the FBI are just stupid, or maybe the plant in the FBI just says, "OoooOOOoooh, we sure gotta find this guy! Let's have a statewide manhunt!" You don't have to lie and cover up when doing dumb things will suffice.

As an addendum, I have never ever seen such incredibly high throughput shill posts about this event on r/conspiracy. There is a 0.0% chance whoever this person is could arrange such a thing, ruling out the "lone gunman" theory absolutely.

These posts are identifiable because only about 3 out of a thousand would have the slightest chance whatsoever to lead someone to the above scenario. The water isn't muddied, "They" filled in the pond.