News is still spotty, and early reports from an event like this should always be taken skeptically, but the basic outlines of the story appear to be these:

A gunman disguised as a policeman opened fire earlier today at a camp for young activists affiliated with Norway’s Labor Party, a center-left party which is the leading member of Norway’s governing coalition. The campers, who were apparently on an organizing retreat, were in their mid-teens, and reports suggest that as many as a dozen — and perhaps many more — have been killed.

Initial claims as to the identity of the shooter have been confused and contradictory.

Update | Police have released new details on the Utoya massacre, and now say at least eighty people have died there. A white Norwegian with reported ties to far-right groups is in custody, as officials attempt to determine whether he had accomplices in the attacks.