He does this thingwhere he holds his breath until his faceturns completely red

When Andrew Briggman—a young soldier in the US invasion of Afghanistan—witnesses other recruits killing innocent civilians under the direction of a sadistic Sergeant, he considers reporting them to higher-ups. However, the heavily-armed and increasingly-violent platoon becomes suspicious that someone in their ranks has turned on them, and Andrew begins to fear that he'll be the next target.