 Whether or not he knew if there was one of the local sniper teams that was on the roof. Because he was probably like a Secret Service guy. And in that building, they had a local team that was there. Oh yeah, so they don't want to shoot a friend. He probably wanted to make sure that there wasn't a friendly on top of the roof. Unless they have really good communication and they knew that they were looking for a suspicious guy that was crawling on top of the roof at that time. I'm not sure.