Anders Behring Breivik Decision

It seems strange that a man who shot and killed 77 people and then apologised for not killing more is declared 'sane' but the Norwegian Courts decision on Anders Behring Breivik seems more to do with any other verdict leading to his sentence being served in a psychiatric hospital rather than prison.
Sentencing him to the 21 years which is the maximum allowed under Norwegian law, he will probably spend the rest of his life behind bars with the justice system increasing his sentence in five year increments.
The problem the court had was if it was decided that Breivik suffered from a mental illness such as paranoid schizophrenia as a psychiatrist originally described him in the trial, then Breivik would be relieved of his legal responsibility for the crime as the law states that the defendant must be deemed mentally responsible when considering culpability and punishment.
To most of us, the actions and words from Breivik to explain his actions showed that he was not 'normal' and by definition, anyone who commits a crime as horrendous as this has some severe mental issues and they are a clear threat to society.
The problem is as one of the lawyers explained while they were waiting for the decision: 'If he is mad, if he is not responsible, if he is not guilty then that means we will have to pity him' which sums up the crux of the moral problem that is Breveik being punished for having a serious mental health problem and as such, should he be treated accordingly by mental health professionals or is it correct that he is treated as a criminal first and foremost and punished accordingly or do we not care one way or another as long as he is locked away somewhere?