American troops had been clashing regularly with Al Mahdi militiamen in the restive Baghdad slum. So when Staff Sgt. Cardenas Alban of Carson saw an object fall from a garbage truck in the distance, his company took positions around the vehicle and unleashed a barrage of fire from rifles and a 25-millimeter cannon atop a Bradley fighting vehicle. The truck exploded in flames.
As soldiers from the 1st Battalion, 41st Infantry Regiment, approached the burning vehicle, they did not find insurgents. The victims were mainly teenagers, hired to work the late shift picking up trash for about $5 a night, witnesses said.
Medics scrambled to treat the half-dozen people strewn around the scene. A dispute broke out among a handful of soldiers standing over one severely wounded young man who was moaning in pain. An uninjured Iraqi claiming to be a relative pleaded in broken English for soldiers to help the victim.
But to the horror of bystanders, Alban, 29, a boyish-faced sergeant who joined the Army in 1997, retrieved an M-231 assault rifle and fired at the wounded man.
Seconds later, another soldier, Staff Sgt. Johnny Horne Jr., 30, of Winston-Salem, N.C., grabbed an M-16 rifle and also shot the victim.
The killing might have been forgotten but for a U.S. soldier who days later slipped an anonymous note under the door of the unit's commander, Capt. Robert Humphries, alleging that "soldiers had committed serious crimes that needed to be looked at."
U.S. officials have since characterized the shooting as a "mercy killing," citing statements by Alban and Horne that they shot the wounded Iraqi "to put him out of his misery."
Military attorneys, however, are calling it premeditated murder and have charged the two sergeants, saying the victim's suffering was no excuse for the soldiers' actions.
"I have no doubt that's why they did it," said Capt. John Maloney, one of the military attorneys prosecuting the case.
"But it still constitutes murder."
Military attorneys in Baghdad said they were unaware of any legal precedent justifying "mercy killing" in a war zone, though such circumstances could be considered during sentencing.
Iraqis who witnessed the Aug. 18 shooting said that rather than provide medical help to an injured civilian, the soldiers treated the Iraqi as if he were an animal struck by a car.
"We are not sheep," said Emad Raheem, 40, who said he was the driver of the dump truck. "We are human beings."
Seven Iraqis were killed in the attack, including the one who was shot, military officials said. Eight others were wounded.
Alban and Horne -- both on their second tour in Iraq -- and their attorneys declined to comment. In statements to military investigators, both acknowledged shooting the Iraqi but have not entered formal pleas. They are facing Article 32 hearings in Baghdad, which will determine whether there is enough evidence to begin court-martial proceedings. If convicted, the soldiers could receive the death penalty.
The case -- one of about a dozen murder cases filed against U.S. troops in Iraq -- is fueling a debate about the conduct of American forces here and the treatment of Iraqi civilians, particularly in the aftermath of the Abu Ghraib prison scandal.
Two other soldiers in Alban's unit, from Ft. Riley, Kansas, also are under investigation for what military officials say were the premeditated murders of three Iraqi civilians in separate cases.
In September, a U.S. reservist was sentenced to 25 years for killing a teenage Iraqi national guard soldier after a sexual encounter in an observation tower. The soldier said he lost control because of traumatic memories of childhood abuse, but family members of the victim accused the American of assaulting the Iraqi and then shooting him to cover it up.