I have been reading this thread with interest and agree with most of what dawndonna has said, and also JakeBullet's comment above.
I don't know why these two boys did what they did, but I am convinced that their upbringing was seriously at fault. Violent criminals can come from all sorts of backgrounds. However, I don't believe that a child who has always been loved, respected, taught to show empathy, work towards rewards rather than have everything handed to them, respect boundaries... I don't believe a child raised that way would treat another human like an object to be used.
I think there are two important things here:
We (society) should be putting a lot more energy and money into identifying and supporting families who struggle with parenting for whatever reason.
We should also be looking very very closely at how we can reduce the rate of reoffending. And if that prison in Norway is achieving good results, that seems like a good place to start. Surely it's more important to prevent crime than it is to punish criminals?