Read the same link you posted. The shot Khadr in the back as he knelt down in a prone position... another man was lying unconsious and was shot in the head.. pretty clear in that account.
The fact that Khadr had his back to them does not mean he was no longer a threat and the other guy was not unconcious.
There is no indication that they were complying with commands when they got shot.
You are a biased presumptuous idiot.
OC-1 reported that although he didn't hear any gunfire, but the dust being blown from an alley on the northside of the complex led him to believe the team was under fire from a shooter between the house and barn. He reported that a grenade was also "lobbed" over the wall that led to the alley and landed 30–50 metres from the alley opening. Running towards the alley to escape the grenade which he also didn't hear detonate, OC-1 fired a dozen M4 Carbine rounds into the alley as he ran past, although he couldn't see anything due to the rising dust clouds. Crouching at the southeast entrance to the alleyway, OC-1 could see a man with a holstered pistol moving on the ground next to an AK-47, with two chest wounds. From his position, OC-1 fired a single shot into the man's head, killing him.
Two soldiers kneel over the wounded Khadr.
When the dust cleared, OC-1 saw Khadr crouched on his knees facing away from the action and wounded by shrapnel that had just permanently blinded his left eye, and shot him twice in the back.