The first thing to note is the background of the event: the major Shi'ite religious festival was taking place, and 8,000 extra Iraqi 'security personnel'were in the area.
And yet, amongst all this heightened security, the ambushers, who were 'disguised' as Americans and who drove 'American-style' vehicles, were waved through checkpoints and conducted a twenty-minute surprise attack including sound bombs, with no apparent response from nearby security forces, even as they drove back through the checkpoints.
At the time it was reported:
Some police commanders in Babil Province and Mr. Khazaali said that bodies of Americans were found in one of the vehicles, but American military officials said they were not missing anyone, and other police commanders in Babil said the men found in the vehicle were gunmen.
Only reported later was the fact that a top official's license plate stolen from the Green Zone was on one of the vehicles, and that an informant claimed that 'high officials' were involved.
They then proceeded to drive to another province, and abandoned the cars in a Sunni area.
They were probably Shi'ite, trying to blame the Sunni. If they had been Sunni, the more effective attack by far would have been against the Shiite population (millions are in attendance) at the most sacred ceremony in the Shiite ritual.
So, believing it to be a Shiite operation, my theory is that it was either al-Sadr, whose top aide had been seized in a raid just a couple days before, or more likely, the Iranians, who also had 5 people seized by the Americans in the days preceding, or as a challenge to the Delta Force operations just launched against Iranians in Iraq.
NOTE: The AP story only talks about 4 dead. The DOD reports 5 died in the ambush. You can see their pictures and read their stories at the links:
Shawn Falter, aged 25
Bryan Chism, aged 22
Brian Freeman, aged 31 (see Snarcalita's addition on John Kerry's comments regarding his encounter with with Brian Freeman in Iraq)
Jonathan Millican, aged 20
Jacob Fritz, aged 25
UPDATE 1/26 12:09pst
Following a press conference with Defense Secretary Gates, CNN reports that Gates said he was unaware of the situation until today. CNN further reports that 1 soldier was killed and 3 wounded in the initial ambush, and that 4 were discovered in or near the abandoned vehicles. Two were handcuffed together in one vehicle, shot to death. One was in another vehicle, shot to death. The fourth was in the vehicle, or nearby, but alive. He died on the way to the hospital.
This diary by Spread the Word: Iraq-Nam, a daily blog on Iraq.