How did it come to light? Did one of his comrades inform on him? I haven't been in his position so I don't know what his motivations were, but he knew that he was doing wrong because he deliberately made sure the British helicopter and the observation balloon were not looking, and he told his men to keep it quiet, and the fact that he kept a recording of his crime is worrying. It's hard to say that he was totally wrong because he had experienced things we haven't, but he was a British NCO who was there to help Afghanistan, and he ended up killing a wounded enemy, knowing that he was in the wrong.