Mass killer Anders Behring Breivik has been sentenced to prison for killing 77 people in the brazen shooting rampage in Norway last year.

A five-judge panel convicted the 33-year-old Breivik of terrorism and premeditated murder. They ruled he was sane enough to be held responsible for his actions.

The judges sentenced Breivik to a maximum of 21 years in prison, the longest sentence allowed under Norwegian law.

But they also issued a special sentence that allows authorities to keep him locked up for as long as he's considered dangerous. He will be kept in solitary confinement in Ila Prison on the outskirts of Oslo, Reuters reported.

According to the report, his prison quarters include a separate exercise room, a computer, and a television.

Breivik confessed to the attacks during the trial. Before the decision, his lawyers said he would accept a prison sentence and would only appeal if the judges ruled him insane.