Although there is some skepticism to the contrary, it appears the Norway massacre self-confessed perpetrator, Anders Breivik, acted alone.
He was an angry, delusional young man with a murderous bent, and the FBI wants American law enforcement to be aware that there is a possibility of something similar happening here.
In a joint FBI/Department of Homeland Security memo (PDF), it states:
"Small-arms operations could be employed through a range of tactics from a lone offender--as illustrated by the recent 22 July 2011 lone shooter attack that took place in Norway--to a coordinated small-unit attack involving several operatives. Recent lone offender attacks and plots in the United States and abroad illustrate the effectiveness of the small-arms tactic and the need for continued vigilance and awareness of this tactic. Attacks by lone offenders--which by definition lack co-conspirators, and therefore provide fewer opportunities for detection--may be more difficult for law enforcement and homeland security authorities to disrupt."
Examples cited by the memo include the soldier from Fort Hood arrested on July 27 of this year with materials to produce a bomb; The lone gunmen who killed two U.S. Airmen at the Frankfurt, Germany, airport on March 2 of this year; and the Fort Hood shooter, Maj. Nadal Hassan, who killed 12 with two pistols in a late 2009 rampage.
The domestic "Lone Wolf" threat is far from limited to Islamic-linked individuals, too. As reported by "60 Minutes," the "Sovereign Citizens" movement - a loosely knit group that doesn't pay taxes, carry driver's licenses or hold Social Security cards - has shown a violent and sometimes murderous dislike of law enforcement. Oklahoma City bomber Timothy McVeigh had only two known co-conspirators.
The use of small, tactical teams - or even well-armed individuals - is also increasingly employed by foreign terrorist groups, and has been used to deadly affect throughout the Middle East and other danger zones.
The overall rise in such cases led the FBI and DHS to conclude "that transnational terrorist groups and homegrown violent extremists (HVEs) could employ small-unit assault tactics in the United States."
Some of the steps they recommend law enforcement use to prevent such incidents include randomizing security patrols in potential target areas, increased reporting of suspicious activity, and conducting increased sweeps for explosive materials.
"We face an increased challenge in detecting terrorist plots underway by individuals or small groups acting independently or with only tenuous ties to foreign handlers," the FBI/DHS memo states. "Recent events have illustrated that state, local, tribal, and private sector partners play a critical role in identifying suspicious activities--such as unusual purchases of or inquiries about firearms, gunpowder, or ammunition--and raising the awareness of federal counterterrorism officials."