Looks as though he could actually spend his natural life in prison. http://en.wikipedia.org/wiki/Life_imprisonment_in_Norway
Certainly, it must of been well planned. He couldn't of just turned up on the day and remembered he was carrying a firearm and saw an opportunity of some kind. He did it and has no remorse, there doesn't always have to be a motive. Anders is just a crackpot that wanted a taste of blood.
Yeah. It is a mental dysfunction of sorts to plan to go out an kill, especially something like this, where the killer knew there'd be numbers, with nowhere to run. If you call it a 'glitch in the brain', no matter what behaviour is shown for the next 50 years or whatever, that glitch can recur. He simply cannot be released, ever.