An important point to remember

Norway's legal system, being geared towards rehabilitation and softer sentencing, means that a flat murder conviction would not automatically suggest a long prison sentence. In fact, it is likely he would not have served his entire life in prison even having killed 77 people. However, as he was determined to be schizophrenic, he can be held until such time as he is determined to be healthy again, meaning he would've had a much better chance of returning to the streets eventually if he had been determined competent and served his sentence out. Schizophrenics do not have a high cure rate, but they can be treated and controlled.