@Fido,
The Norwegian ultra-right could be behind these attacks, even if it was simply a lone wolf, but each time these attacks occur, a great number of people assume Islamists were involved and a small group of people castigate them for prejudice. At the same time, this same small group of people assume (or hope) that right-wingers are involved.
Far more times, than not, the attacks involve Islamists, not right-wingers, and yet the "small group" keeps castigating and hoping.
Sooner or later a blind squirrel finds an acorn. Perhaps the acorn is Norwegian.