What I find weird is that the area where he accessed the roof was apparently a police staging area. Basically, the guy waltzed through a police staging area with a long gun and shot the president.
I just spent a while googling it, and nothing looks conclusive at all. But looks like Snopes has it as false as least.
But as far as the downvote, just saying "you're wrong" is not helpful in the slightest. Maybe include a source, or even just an explanation that there was some early misinformation going around, and doesn't look likely at moment.