Sadly, a lot of this was in a U.S. run facility, the general in charge has been relieved and placed under hack. She is up for a general court martial, and the attending punishment.
However, this conspiracy theory of these acts being committed by "mercenaries" at the behest of "unnamed" leaders in Washington is really a bit absurd, don't you think? See above. U.S. military controlled facility. And they bring terrible shame on good soldiers, besides providing inspiration to Al Jazeera and the insurgents. The guilty will not pay enough, and the good soldiers will have to deal with the aftermath.
Another unfortunate part of this is that evidently the British have their own problem of this ilk. Saw some headlines, but haven't read the articles as yet.
This is something that is fueled by anger and hatred. Some cannot deal with their emotions and desires. There is no excuse for the behavior, and I'll make none for it. One reason behind the behavior is the atrocities committed against captured, wounded, or killed coalition soldiers. I said REASON, I did NOT say EXCUSE. Those atrocities were well publicized and not soon forgotten. Unfortunately, these crimes against POW's (assuming they were indeed captured uniformed soldiers of the Iraqi military) will also not soon be forgotten.