There was absolutely no way Ian Smith was suffering from posttraumatic stress disorder. He was sure of it.

He was O.K. He was living with his girlfriend in a suburb of Nashville working three jobs — mowing lawns, delivering pizzas, cleaning a local church. He was carrying a 4.0 average at Volunteer State Community College. Yes, he’d seen some terrible stuff during two tours in Iraq. But others had been through much worse. He’d never been wounded. He was alive.

But it was a strange sort of alive. He lived on his couch, with his pistol. He didn’t sleep much. The only way he could get to sleep was by getting drunk, so he got drunk every night and slept with his gun under the pillow. He had gained 60 lb. since leaving the Army in February 2009. He drank more and more. His girlfriend left him. He put the gun…