It's a good theory. Unfortunately no other weapons (apart from a single AK-47 - which was commonly carried in 2007 Baghdad) or bombs were found, so I can just as easily say that they might have been aliens from Xenu.

I do think that there are more extenuating circumstances than some may think (it was 2007 in Baghdad - people forget how bad things were there). But claims that those people were anything other than a random group of people will require some evidence.