I have seen it mentioned in a lot of places that the shot came from the roof of the Losee building.
https://www.aljazeera.com/news/2025/9/11/when-and-where-charlie-kirk-was-shot-a-visual-timeline
There is also video of a man prone on the rooftop before the shooting and then someone running on the roof right after the shot.
I think its pretty unlikely that some rando did this, but who knows. The skill level to get this shot off with such accuracy though and the ability to escape without a decent picture being taken of the shooter by a security camera or something shows an immense amount of planning. I think to escape like this would require help, it would require mapping out an escape plan so you know where the cameras are. I think its very unlikely that some lone wolf would be able to pull all this off.