The Counter Snipers shown on multiple videos were on a roof behind and to the left of the podium, if you were facing the podium. Their view of Crooks was obstructed by a tree. It seems that there was another Counter Sniper team on the top of the building on the far right behind the podium. I have never seen a video showing this position. But, this position would have had a view of Crooks if he had his head above the crest of the roof...it did not have a tree in the way. This second Counter Sniper team is supposed to be the one that took Crooks out and the claim of 400 yards or so seems to match.
The video from the rooftop is body cam footage. The cop with the body cam says that Greg from the Beaver County sniper team took and distributed photos of the shooter and that Greg is currently inside the sniper perch that was behind the shooter. So a Beaver County sniper is inside that window at the time this video is taken, but other snipers may have been manning the window earlier when the shooting happened.