I agree with a commenter who said it looked like the police snipers had the shooter in their sights but waited until after he fired (and presumably killed Trump) before they took him out.

https://www.lewrockwell.com/2024/07/no_author/secret-service-has-some-splainin-to-do/

Secret Service Has Some 'Splainin To Do
Zero legitimate explanation for how a man with a rifle got onto a roof only 120 meters away from Trump with a clear line of sight.

By John Leake

As I have observed in previous columns, our era in the United States is frequently beset with incidents characterized by a catastrophic loss of competence. Decades of procedural knowledge seem to vanish from one day to the next, leaving sensible people wondering how it could possibly happen.

The attempted assassination of Donald Trump this evening at the the Butler Farm Show Grounds is a perfect example of this bizarre phenomenon. The shooter climbed onto the roof—purportedly with an AR-15 style semi-automatic rifle —120 meters from Trump on the stage. From this vantage point, he had a clear line of sight for a shot that would have been easy for even a middling marksman. The following aerial photograph shows the shooter’s position relative to Trumps.

As anyone who understands the rudiments of security knows, the FIRST thing you do is secure all rooftops within sniper range. Note in the following video that a counter sniper (with the word POLICE embroidered on the back of his vest) on the roof behind Trump is scoping the would-be assassin’s position. ......