LONDON (AP) -- A royal marine murdered an injured insurgent in Afghanistan by shooting him in the chest at close range, a British court martial board found Friday. According to prosecutors, he told fellow soldiers to hush it up and acknowledged "I just broke the Geneva Convention."
The board ruled that the commando, who can only be identified as Marine A, was guilty of killing the unnamed man in Helmand Province in September 2011.
"It is a matter of profound regret in this isolated incident that one marine failed to apply his training and discharge his responsibilities," Brigadier Bill Dunham, of the Royal Marines, said in a statement. "It was a truly shocking and appalling aberration. It should not have happened and it should never happen again."
Prosecutors said the incident took place after a military base in Helmand Province was attacked by two insurgents. A helicopter opened fire in response, and Marine A, together with two other British soldiers, then discovered the injured Afghan in a field.
The three moved the man to a sheltered area. Marine A shot the Afghan in the chest with a 9 millimeter pistol, before quoting a phrase from Shakespeare as the man died before him, according to prosecutors.
"Shuffle off this mortal coil ... It's nothing you wouldn't do to us," the marine was heard saying in a video that captured the incident. The footage was inadvertently recorded by a camera mounted on the helmet of Marine B.
He then turned to his comrades -- identified only as Marines B and C -- and said: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."
Marine B then replied: "Yeah, roger, mate."
Earlier in the trial, prosecutors called the killing a "field execution."
The soldiers told their superiors that the man had died from wounds, but the killing came to light when police investigating other matters found the video on a soldier's laptop. Footage was shown at the court martial.
The three denied murdering the Afghan, and one marine had said he believed the man was already dead.
But a seven-member board convicted Marine A after a two-week trial. The two other marines were acquitted of "encouraging and assisting" in the killing.
The convicted soldier will be sentenced on Dec. 6. The maximum sentence is life imprisonment.
British forces have been fighting the Taliban in Afghanistan alongside other international forces since 2001. The U.K. plans to end its combat role there by the end of 2014.
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