When Army investigators tried to interrogate Staff Sgt. Calvin R. Gibbs in May about the suspected murders of three Afghan civilians, he declined to answer questions. But as he was being fingerprinted, Gibbs lifted up his pant leg to reveal a tattoo.

Engraved on his left calf was a picture of a crossed pair of pistols, framed by six skulls. The tattoo was "his way of keeping count of the kills he had," according to a report filed by a special agent for the Army's Criminal Investigations Command. Three of the skulls, colored in red, represented kills in Iraq, Gibbs told the agent; the others, in blue, were from Afghanistan.

Gibbs said he acted in self-defense each time, but Army officials came to a different conclusion. They have charged him with conspiring with other soldiers from the 5th Stryker Combat Brigade of the 2nd Infantry Division to murder three unarmed Afghans, allegedly for sport, and dismembering and photographing the corpses.

The war-crimes investigation is the gravest to confront the Army in Afghanistan since the U.S.-led invasion in 2001. In echoes of the Abu Ghraib scandal that unfolded from Iraq in 2004, the Army is scrambling to locate dozens of digital photographs that soldiers allegedly took of one another posing alongside the corpses of their victims. Military officials worry disclosure of the images could inflame public opinion against the war, both at home and abroad.

In addition to Gibbs, 25, the Army has charged four other soldiers with involvement in the killings, which took place between January and May in Kandahar province. So far, the Army has released limited information about the case, although a pretrial hearing for one of the accused soldiers began this week at Joint Base Lewis-McChord, Wash., home of the Stryker Brigade.

Summaries of Army investigative reports obtained by The Washington Post provide previously undisclosed details about how the murders were allegedly committed and covered up. The reports also indicate that a fourth unarmed Afghan was killed. And they show that soldiers in Gibbs's unit - 3rd Platoon, Bravo Company, 2nd Battalion, 1st Infantry Regiment - have given sworn statements in which they assert that he was the one who came up with the idea of targeting Afghan civilians at random and developing cover stories.

Gibbs's civilian defense attorney, Phillip Stackhouse, did not return phone messages seeking comment. He has previously told reporters that the killings Gibbs has been charged with were combat-related and therefore justified. Attorneys for the other accused soldiers have also denied wrongdoing.

Conflicting reports



According to Army investigative reports, Gibbs and other members from his unit shot and killed the fourth unarmed Afghan on Jan. 28. Some soldiers told investigators that platoon members planted ammunition next to the body so their superiors would rule the shooting justifiable.

Two soldiers told Army special agents that their patrol came upon the Afghan as he was sitting along Highway 1 in Kandahar. According to the statements, Gibbs and another soldier fired warning shots at the man's feet; other soldiers then opened fire as well, killing the Afghan.

Army criminal investigators later decided not to press murder charges, citing soldiers' stated fears that the Afghan may have been a suicide bomber and determining that they had given appropriate warnings before using deadly force.

According to the two soldiers' statements, however, the Afghan made no aggressive movements and there was no sign he was armed. Some unit members said they placed a magazine from an AK-47 rifle next to the corpse "to give the appearance the Afghan was an insurgent," according to an investigator's report.

Officials at Joint Base Lewis-McChord, near Tacoma, Wash., declined to explain why the Army did not file charges related to the Jan. 28 killing. They also declined to comment on the fresh disclosures in the criminal investigative reports.