From the muzzle sound of the shooter i.e from the first of the 4 shots till the muzzle sound of the SS sniper the time delay is 17 seconds. In the Video the bystander who was recording only said he is down after the SS shot him after 17 seconds.Iirc 1.5-2 second reaction time for a concealed carry to ready is considered very good.
The key issue here .. is that roof should have been watched over .. and clearly if it had been, the threat could have been neutralized before he got over the crest of the roof.
That and the fact that the shooter was in a Blackrock Ad, I don't buy the reason of lack of manpower or even DEI hires.
I bet the deepstate encourages such would be lone wolves online and gives a wink and a nod and also making a window by clearing the path.