So they knew exactly which floor. Didn’t they say at the beginning they weren’t sure which floor? That they had to search for him & that’s what took so long?
Someone called at 10:08? saying he could see the flashes in one of the upper floors. We don't the entirety of the phone call.
Now remember, it's a busy place...if calls are coning in bing, bing, bing....whoever picks it up doesn't know if there's a more important one "someplace".
And after the volley began, everything turned to chaos.