The deaths of the two Iraqi Christians - including one who used the white sedan as an unofficial taxi to raise money for her family - came a day after an Iraqi government report called on the U.S. to sever all contracts in Iraq within compensation to the families of those killed in the Sept. 16 incident. CBS News has found the Iraqi witness accounts of the shootings are remarkably consistent.
The deaths Tuesday at a Baghdad intersection may sharpen demands to curb the expanding array of security firms in Iraq watching over diplomats, aid groups and others.
"We deeply regret this incident," said a statement from Michael Priddin, the chief operating officer of Unity Resources Group, a security company owned by Australian partners but with headquarters in Dubai in the United Arab Emirates.
Priddin said the company would disclose more details of the shooting after "the facts have been verified and the necessary people and authorities notified." Priddin would not comment on whether his guards killed the women.
But initial accounts - from company statements, witnesses and others - suggested the guards opened fire as the car failed to heed warnings to stop and drifted closer to the convoy near a Unity facility in central Baghdad's Karrahah district.
It was not immediately clear whether the guards were protecting a client at the time, but a group that uses its security agents said its personnel were not at the scene.
Four armored SUVs - three white and one gray - were about 100 yards from a main intersection in the Shiite-controlled district. As the car, a white Oldsmobile, moved into the crossroads, the Unity guards threw a smoke bomb in an apparent bid to warn the car not to come closer, said Riyadh Majid, an Iraqi policeman who saw the shooting.
Two of the Unity guards then opened fire. The woman driving the car tried to stop, but was killed along with her passenger. Two of three people in the back seat were wounded.
Priddin's statement offers a similar account: "The first information that we have is that our security team was approached at speed by a vehicle which failed to stop despite an escalation of warnings which included hand signals and a signal flare. Finally shots were fired at the vehicle and it stopped."
Iraqi police investigators said they collected 19 spent 5.56mm shell casings, ammunition commonly used by U.S. and NATO forces and most Western security organizations. The pavement was stained with blood and covered with shattered glass from the car windows.
In other developments: