In dramatic testimony at Camp Pendleton Marines' base in southern California, Melson Bacos said he had watched in horror as 52 year old Hashim Ibrahim Awad was bound and gagged before being gunned down.
Bacos, testifying after a plea deal that saw him admit to kidnapping but cleared of murder charges, said the April 26 killing in Hamdania had arisen out of frustration at the reputed release of a "known terrorist".
He said that during a patrol to look for roadside bombs, squad member Lawrence Hutchins formulated a plan to go to the suspected insurgent's house to "get him."
If the plan failed, the Marines would "find someone else," Bacos said.
After failing to locate their intended target, the Marines raided the house next door, Bacos said.
Two Marines pulled Awad outside and took him to a hole that had been dug to look like one used for roadside bombs, he said.
The Marines grabbed a shovel lying outside another home, then went inside and grabbed an AK-47 assault rifle, Bacos added.
He said Hutchins ordered the Marines to fire AK-47 rounds into the air "to make it look like we were in a firefight with this man."
Hutchins fired the first few shots, then other Marines fired rounds, Bacos said.
Another soldier, lance corporal Robert Pennington, wiped fingerprints off the assault rifle, he said.
The Marines then bound the hands and feet of Awad and gagged him before firing three shots into his head, Bacos said.
Hutchins then radioed headquarters and reported that his squad had killed a man in a firefight.
Sick to the stomach
Bacos, a Purple Heart recipient who is the son of immigrants from the Philippines, said he felt "sick to my stomach" following the killings and said he had tried to intervene.
Bacos has been sentenced to 10 years in prison, but he will end up serving only a year under a plea deal.
Military Judge Col. Steven Folsom issued the sentence to the 21 year old who has also been dishonourably discharged.
Bacos agreed to a plea deal earlier today in which he agreed to testify in exchange for a lesser sentence.
Under the deal, he will end up serving no more than one year in confinement.
Relatives of Awad claim he was murdered after refusing to act as an informer for the US military. The judge planned to view videotaped interviews with Awad's family before the hearings resumed.
Two of the seven marines involved in the case, John Jodka and Marshall Magincalda, on Wednesday pleaded not guilty to murder.
Jodka, a 20-year-old private, will stand trial on March 5, following the completion of Magincalda's court martial, which gets underway on February 1.
Five other Marines involved are yet to stand trial.