The suspect has now stated that he had accomplices. Police are investigating his claims that "two more cells" existed in his organisation. This could be a delay tactic, given that he initially said he was working alone, but sadly I would not be at all surprised if there are other parties. We'd all like to believe that these kind of attacks are the work of "one madman", but often, that's not the case.
I watched news coverage from Oslo earlier, and the sight of the hundreds of flowers laying on the ground was incredibly moving. The sheer scale of this is hard to comprehend.