The other night on cable TV I watched I Shot My Parents, a BBC documentary about a 14-year-old boy who walked into his parents’ bedroom in the middle of the night and shot each of them three times in the head. This happened in Moses Lake, Washington, in 2013. The boy, Nathon Brooks, was a seemingly cheerful, seemingly well-adjusted basketball star at the local high school. Under police interrogation he cooked up a story about hearing screams, seeing a man moving through the house, and hiding until the coast was clear. When he was told that the security cameras in the house had picked him up running around in his underwear with a gun in his hand, he broke down and confessed, and though he couldn't say why he had shot them, he did say that just before he shot his mother the thought had flashed through his mind that he didn't have to do what he was about to do and that afterwards, when he sat alone on the staircase, he understood that he had done something awful.