That Anders Breivik was a regular player of violent video games does not explain why the Norwegian became the calm killer of 77 mostly young people, many of whom would have shared his gaming passion.
An obsession with games such as World of Warcraft might seem a plausible explanation for why the apparently unremarkable 33-year-old, now on trial for murder in Oslo, came to carry out the shooting spree and bomb attack last July, but it is a dangerous simplification driven by our need to understand.
People want an answer for why these thing happen. That's completely understandable, said Seena Fazel, a consultant forensic psychiatrist at Britain's University of Oxford. That's also why mental illness is often an attractive avenue, because it does seem to provide some sort of answer.
The motive, in part, is to understand what distinguishes a mass killer from the rest of us, experts say. Breivik's game-playing, however, doesn't do that.
Tore Sinding Bekkedal, who escaped unharmed from the island of Utoeya while Breivik carried out the shooting, told Reuters he found it baffling to link computer games to the attack.
I've played the same violent video games, and I don't go around shooting kids. Half the people on Utoeya played that same game ... It's an established part of youth culture, he said.
CORRELATION OR CAUSATION?
Breivik told the court he once played Modern Warfare for 17 hours straight, and that he used such computer games to work out the police response and his best escape strategy.
Fazel points to a 2008 paper in the journal Criminal Justice and Behaviour, which he says is one of the most cited studies in this research field and which describes two experiments designed to test whether violent games encourage violence.
The results showed that while males were more aggressive than females, neither exposure to violent-video-game conditions in a laboratory, nor previous real-life exposure to violent video games caused any differences in aggression.
The researchers concluded that trait aggression, family violence, and male gender were predictive of violent crime, but exposure to violent games was not.
Correlation is often wrongly confused with causation, says Christopher Chambers, a senior research fellow at Cardiff University's School of Psychology.
If a person plays violent video games and then commits acts of violence, it doesn't prove that the video games caused the violence. There could be no link whatsoever, or it might even be the other way round: that the person's violent tendencies drew them to violent video games in the first place, he said.
In World of Warcraft, players create and control a character in an online world, fighting battles and completing quests for rewards. Since its launch in 2004, it has earned a reputation as one of the world's most addictive computer games and has already been linked to criminal acts.
In June last year an American mother was jailed for 25 years after her three-year-old daughter died from malnutrition while she played the game for hours on end.
But, says Henrietta Bowden-Jones, consultant psychiatrist in addictions at Imperial College London, while World of Warcraft is notorious as highly addictive and as a game that features in the lives of some patients with compulsive Internet use, it cannot be blamed for Breivik's killing spree.
World of Warcraft is not necessarily creating but attracting people who may be finding it difficult to fit in with their peer groups, she told Reuters.
Obsessive game playing for such people can therefore be a symptom of their discomfort with reality.
Thomas Hylland Eriksen, professor of social anthropology at the University of Oslo, said Breivik's testimony shows how much he needed to build an alternative reality for himself, something he extended to the real world when he donned a homemade uniform and went out to kill.
He likes order, he doesn't like impurity and chaos and he's obsessed with boundaries, Eriksen said.
When he puts on his uniform, he's no longer the lone, slightly unsuccessful young man from the west end of Oslo who never completed an education, never did really well in real life; he becomes a knight, a defender of civilization, of Europe against the invading Muslims.
(This version of the story has been corrected to fix the fourth reference to game in paragraph 15 as World of Warcraft, not Warfare)
(Additional reporting by Balazs Koranyi, Walter Gibbs and Victoria Klesty in Oslo; Editing by Will Waterman)