As the United States commemorated the 10^th anniversary of the 9/11 attacks, terrorism experts stepped up warnings that authorities must look beyond the usual sources of terror, to the lone wolves stirring with anger and seeking out big-impact weapons.

Isolated and underestimated, lone wolves might go unnoticed even as they try to get chemical, biological, radiological and nuclear weapons – collectively known as CBRN – that can spread terror and spark psychological chaos.

Anders Breivik is the latest of the lone wolves and a point of concern among terrorism experts. His devastating attack in Norway in July spurred researchers to mine his 1,500-page treatise in search of evidence that unconventional, free-agent terrorists may now have greater potential to inflict damage and ignite panic.

Breivik’s manifesto was more than just the ramblings of a lone nut.

“Dismissing Breivik’s “[weapons of mass destruction] idea” as unrealistic is dangerous and overlooks important nuances that give his warnings about greater weapons added validity. Moreover, his writings might spur other extremists, according to a little-noticed report from the Washington, D.C.-based Federation of American Scientists.

Acknowledging the threat

U.S. Homeland Security Secretary Janet Napolitano, in an interview on ABC News last week, said one of the biggest challenges she had seen as DHS secretary, “is movement toward the home-grown violent extremist. The person who, for whatever reason, decides to attack his fellow citizens,

She warned citizens to be vigilant of “the lone actor that we may not know about, who may already be in the United States and so it requires us to be vigilant and the public be vigilant.”