The second-to-last photograph [1] taken by Namir Noor-Eldeen shows an American Humvee and the radio calls make it clear that there is a ground force in the vicinity which was reporting a contact with the individuals on the ground, was able to see the individuals at various points in the action and was close enough that it took only 8 minutes for them to mount up and arrive on the scene. This group (apparently "Bushmaster element") appears to be the one which radios "Yeah, we had a guy shooting. And now he's behind the building" at 04:22.
Your assertion that there were no Iraqi or coalition ground forces in the area is not supported by the video.
[1] http://duckbar.mirror.waffleimages.com/files/c7/c76f1e685afe...