I'm Ocams razor on these things - is it most likely that there was an inside conspiracy in which the President agreed for an unknown guy and registered Republican to shoot at him (close enough to hit him in the ear) whilst everyone else at the federal and state level was ordered to look the other way as part of a false flag - which killed an American citizen as part of what they were doing. Or are people just a bit shit at their jobs sometimes. Particularly when you've done these rallies in little Bumfuck nowheresville multiple times a week for the last four years.

Could it be done as a false flag. Sure. In the same way that you could somehow melt the structural iron of the WTC with thermite. Was it done? I doubt it. I think he was probably a smart kid - but not a great shot. Security personnel probably screwed the pooch and local law enforcement did their usual level of incompetence.