A sergeant in the British Royal Marines was found guilty of murdering an insurgent during a court-martial on Friday, after helmet camera footage of him emerged showing him shooting the man in the chest at close-range. The man, identified only as marine A, faces a life in prison after being found guilty of murder, the Guardian reported. He and two other Royal Marines were on trial for their actions during a Sept. 2011 patrol in Afghanistan’s Helmand province. Royal Marine A was accused of dragging an insurgent who was hit in a helicopter attack to the side of a field…