Investigators say Anders Breivik is not linked to any terrorist cells or right-wing militants. They say the 32-year old had been preparing for some kind of large-scale attack for at least 10 years.
In a manifesto released just before the attacks, Breivik describes in detail how he secured weapons and bomb-making ingredients, including six tons of fertilizer. Most plots fail during that stage, experts say. But Breivik had the discipline to stay totally mum about his plans, which is highly unusual.
"The Norwegians have his computer," said Bob Ayers, a London-based former U.S. intelligence officer. "If there was significant dialogue, there would have been a footprint. Acting alone gave him the advantage of not being watched by security personnel."
The attacks have stirred questions in Europe about whether authorities have neglected the threat of right-wing extremists in their push to crack down on Islamist terror groups after 9/11.
Security officials insist they have not, and statistics from the European police agency Europol show no surge in right-wing terror.
Red Cross and Norwegian rescue workers continue to search the waters off utoya island for bodies of those killed in last week's shooting rampage
The Associated Press contributed to this report.
