I have no idea who stabbed this woman, but I do know that a Norwegian friend and I share news stories from around Scandanavia. Many, many crimes that make it to the news seem to be perpetrated by Muslim immigrants to these countries. Amazingly, they are often let off w/light sentences because they 'don't understand the Nordic culture' - even if they've been in Norway or Sweden for 10 years!
Every country homebrews enough criminals. It would appear to me that the Nordic countries should seriously reconsider continuing to let in a group of people who seemed hell bent on crime and disruption.