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.

No one understood why he had done what he had done: not his parents (who miraculously survived, the mother with impaired vision, impaired hearing and impaired memory, the father fully recovered, at least physically), not his best friend, not the prosecutor, not the defence attorney. The prison psychiatrist diagnosed him with major depressive disorder after ruling out psychosis, adding that despite his happy-go-lucky reputation he was an introvert with bottled-up emotions, angry and resentful at being recently grounded. He pleaded guilty to assault with a deadly weapon and got 15 and a half years. His parents have forgiven him.

In all this, amazingly, it didn't occur to anyone to suggest that one reason the boy had shot his parents – and one reason five are killed by their children every week in the United States – was that the house was full of guns. The boy was surrounded by them. Not too long ago he had shot his first deer. His mother had shot her first at the age of 12 and had her own muzzle-loading hunting rifle in the gun cabinet. They were a gun-toting family. However depressed, angry and resentful Nathon may have been, if there hadn’t been guns in the house, it would never have occurred to him to shoot anyone.

The gun lovers say that guns don’t kill people, people kill people. That’s what they were saying at the NRA’s annual convention in Dallas last week, when they weren’t voting for Oliver North to be their organisation’s new president. The gun haters say that without guns, people wouldn't be killing anyone. To be honest I don't know what the specific retort is to the latter argument. Maybe the gun lovers say that if the criminals and maniacs didn't have guns they'd find other ways to kill, which is doubtful in the vast majority of cases, though I will say that if guns had never been invented, the gun lovers might very well be walking around with sticks of dynamite to throw at targets, animals and even prowlers. Then their 12-year-old children would be taught how to light the fuse and when to throw the thing so that it didn't explode in their faces. In any case, I understand that if you took away their guns (or their sticks of dynamite) these people would feel great deprivation. The rest is bullshit. I mean the arguments about the Second Amendment and self-defence. Trampling on the Constitution never bothered these freedom lovers when it came to African American civil rights or banning books. As for self-defence, the idea that untrained civilians can outshoot armed criminals is preposterous, and a guaranteed recipe for disaster.

What amazes me about the Nathon Brooks case, again, is that while searching for an answer, it did not occur to a single one of the principals to note that the availability of guns in the house was at the very least a contributing factor in the shooting. The gun culture that envelops places like Moses Lake is so pervasive that the act of shooting is as natural as turning on the TV or fiddling with a smartphone. It is always on the menu. It is always an option. That is where the problem begins.