In February, Trump suggested violent video games are partly to blame for mass shootings in America. He’s not alone. One of the experts the White House invited to its closed door meeting today to discuss the effect of violent video games is Dave Grossman, a retired US Army lieutenant colonel and author of the book Assassination Generation: Video Games, Aggression, and the Psychology of Killing. In Grossman’s mind, the media—and video games in particular—are training children to kill.

Assassination Generation is just one of Grossman’s many books. He travels the country training local law enforcement to normalize the act of killing. He once even told a crowd of police in Ohio that it would lead to the best sex of their lives.

One of Grossman’s seminars appears in the documentary Do Not Resist—a film about the militarization of police. In the movie, he described what happens when a cop gets home safe after killing someone.

“They all say, ‘the best sex I’ve had in months,’” Grossman says in the movie. “Both partners are very invested in some intense sex. There's not a whole lot of perks that come with this job. You find one, relax and enjoy it."

It’s not the only outlandish thing he’s said. The New Yorker put together a compilation from the same Ohio seminar here. “Maybe there was a day when a man was asking for an ass whooping, it was a cop's job to give it to him,” Grossman said to a crowd of law enforcement officers. It’s the same logic Trump used when he told a group of police not to worry about injuring suspects during an arrest.

At minute 11, in his three hour lecture called “Bulletproof Mind” , Grossman advocated arming school teachers. “Like Israel, Thailand has found out the only way you keep your schools open is armed teachers and armed parents in the school 24/7.”

“We are at war,” he said at the end of the seminar shown in the documentary Do Not Resist, speaking to police. “And you are on the frontline of that war. When they come to murder the children, the individuals who tried to disarm our cops will be hunted down. Across the nation they will be attacked, they will be spit on, they will be driven deep into their slimy little hole so that they never come out again. There ain't nobody in Russia complaining about the militarization of police."

If that sounds like dystopian vision of the future to you, you're not alone. Grossman's work inspired an episode of Black Mirror , according to show creator Charlie Brooker.

Other than training cops to be more efficient killers, Grossman also tours the country to lecture schools on why video games are the real cause of school massacres.

‘The guns have always been there,” Grossman told Loud Dobbs in a 2012 Fox segment. “The factor that was never there before is violent visual imagery inflicted upon children, particularly the video games.”.

“The only common denominator in all these tragic massacres that have plagued our country has been exposure to violent video games,” he wrote in an editorial for The Daily Beast.