It looks like it was a disturbed person from Norway who had a political agenda but we should know more in the coming days. Violence is very unusual in Norway so it's bound to have a significant impact on the country. The Guardian:
A Norwegian dressed as a police officer killed at least 80 people at an island retreat, police said early on Saturday. It took investigators several hours to begin to realise the full scope of the massacre, which followed an explosion in Oslo that killed seven and that police say was set off by the same suspect.
Police initially said about 10 people were killed at the camp on the island of Utøya, but some survivors said they thought the toll was much higher. Police director Øystein Mæland told reporters early on Saturday they had discovered many more victims.
"It's taken time to search the area. What we know now is that we can say that there are at least 80 killed at Utøya," Mæland said. "It goes without saying that this gives dimensions to this incident that are exceptional."
