In a closely watched war-crimes trial, a 22-year-old U.S. soldier based in Washington state has pleaded guilty to murder and conspiracy in the killing of three unarmed Afghan civilians last year.

"The plan was to kill people," Spc. Jeremy Morlock of Wasilla, Alaska, told an Army judge this morning at Joint Base Lewis McChord, the Seattle Times reports. He stipulated that the deaths, in January, February and May 2010, were staged, with grenades or weapons dropped by the corpses to make them appear to be legitimate combat deaths.

Monday, the German magazine Der Spiegel published details of the killings and featured a photo of Morlock kneeling next to the body of the man he killed in January 2010. The Pentagon apologized "for the distress these photos cause," saying they depicted actions "repugnant to us as human beings and contrary to the standards and values of the United States Army."

Under a plea bargain, Morlock, who served with the 5th Brigade, 2nd Infantry Division in southern Afghanistan , faces a prison term of up to 24 years in exchange for testimony against his squad leader, Staff Sgt. Calvin Gibbs, and three other platoon members. Morlock portrays Gibbs as the ringleader who offered "scenarios" about killing unarmed Afghans.

Gibbs has maintained that all the deaths were the result of combat.