The article text provided contains no actual content — only the headline and site boilerplate ("Your browser does not support iframes… Deep Dive Crime Advertisement Advertisement") repeated twice, with no body text about the events described in the title. I can't produce an accurate summary without the real article content, since inventing details about the 2011 Utøya/Oslo attacks would risk factual errors.

Could you provide the full article text (e.g. by pasting it directly), or try fetching the URL again? If you'd like, I can also attempt a WebFetch of the URL to retrieve the content.