In addition to impairing judgment, causing short-term memory loss, infertility, recently being linked to testicular cancer in men, marijuana is also known to occasionally cause toxic psychosis and greatly exacerbate preexisting psychological conditions, especially those related to anxiety and mood disorders. There have been reported cases of people high on regular, untainted marijuana who have freaked the hell out, gotten violent and murdered someone.
Pot is hardly the harmless, saintly recreation that people who believe and spread the pro-pot propaganda think it is.
That being said, blaming the fact that this guy is an awful human being on either pot or video games is intellectually bankrupt. There's a whole 31 flavors of stupid going on in this story, and the drugs and games barely play into it. He could have been engaged in any other activities - drinking red bull and working on a stamp collection - and those activities would have been ignored by the press and labeled as irrelevant. But because video games and drugs are hot-button, scapegoat issues for moral failings and human ineptitude, they're treated with more focus than they deserve in this article.