The suspect arrested in today's bombing and shooting attacks in Oslo is 32-year-old Anders Behring Breivik, who is believed to have links to right-wing extremist and anti-immigrant (read: anti-Muslim) organizations. (source: Sky News). And now, he has a Wikipedia page. The Daily Mail has photos.
Aftenposten notes that he is said to be a conservative Christian and a Mason, and into hunting and bodybuilding. He owned a farming company that had access to chemicals believed to have been used for bomb-making.
According to comments attributed to him on various Norwegian right-wing/anti-immigrant forums, he was a fan of an array of white supremacist and anti-Muslim pundits—including some from the US. Assuming it's legit, all of this makes early reports that Muslims were responsible for the attacks all the more regrettable.