Brings back some memories. I was working in midtown, but my apartment was 3 blocks South of the trade center. I got back home about an hour after the collapse, and the way I've always described the scene was that it looked like a volcano had erupted because of all of the ash everywhere. The 7th picture in the series is really incredible in showing how big that cloud of ash was when the second tower went down.
Man, I never understood before the problems they must have faced just with people nearby watching and suffering from dust and ash inhalation. It COATED BLOCKS.