In a 1,500 page manifesto, Nowegian shooter Anders Behring Breivik has described using Modern Warfare 2 and World of Warcraft as training manuals.
Breivik, who killed seven people with a bomb and shot a further 86 at a youth camp, claims to be fighting an 'Islamic takeover' of Europe, and was carrying out preparations for his acts for years.
He describes building practice bombs and visiting rifle ranges - but also using video games as training tools.
"I just bought Modern Warfare 2, the game. It is probably the best military simulator out there and it's one of the hotttest games this year," he wrote in February last year.
"I see MW2 more as a part of my training-simulation than anything else. I've still learned to love it though and especially the multiplayer part is amazing. You can more or less simulate actual operations."
As a result, conservative groups are once again calling for more restrictions on violent video games.
"The next time a teenager or young man goes on a murderous rampage, notice how he was first addicted to harmful video games," says the 'trustworthy encyclopaedia' Conservapedia.
In fact, Breivik doesn't seem to have spent much time playing video games - and even says that he's "more the fantasy RPG kind of person - Dragon Age Origins etc, and not so much into first personal shooters".
Indeed, he lists his other interests as 'opera, theatre, art exhibitions'. Do't hear anyone calling for those to be banned, do we?