An officer from a large metropolitan area said that “militias, neo-Nazis and sovereign citizens” are the biggest threat we face in regard to extremism. One officer explained that he ranked the right-wing threat higher because “it is an emerging threat that we don’t have as good of a grip on, even with our intelligence unit, as we do with the Al Shabab/Al Qaeda issue, which we have been dealing with for some time.” An officer on the West Coast explained that the “sovereign citizen” anti-government threat has “really taken off,” whereas terrorism by American Muslim is something “we just haven’t experienced yet.”

Last year, for example, a man who identified with the sovereign citizen movement — which claims not to recognize the authority of federal or local government — attacked a courthouse in Forsyth County, Ga., firing an assault rifle at police officers and trying to cover his approach with tear gas and smoke grenades. The suspect was killed by the police, who returned fire. In Nevada, anti-government militants reportedly walked up to and shot two police officers at a restaurant, then placed a “Don’t tread on me” flag on their bodies. An anti-government extremist in Pennsylvania was arrested on suspicion of shooting two state troopers, killing one of them, before leading authorities on a 48-day manhunt. A right-wing militant in Texas declared a “revolution” and was arrested on suspicion of attempting to rob an armored car in order to buy weapons and explosives and attack law enforcement. These individuals on the fringes of right-wing politics increasingly worry law enforcement officials.

Law enforcement agencies around the country are training their officers to recognize signs of anti-government extremism and to exercise caution during routine traffic stops, criminal investigations and other interactions with potential extremists. “The threat is real,” says the handout from one training program sponsored by the Department of Justice. Since 2000, the handout notes, 25 law enforcement officers have been killed by right-wing extremists, who share a “fear that government will confiscate firearms” and a “belief in the approaching collapse of government and the economy.”

Despite public anxiety about extremists inspired by Al Qaeda and the Islamic State, the number of violent plots by such individuals has remained very low. Since 9/11, an average of nine American Muslims per year have been involved in an average of six terrorism-related plots against targets in the United States. Most were disrupted, but the 20 plots that were carried out accounted for 50 fatalities over the past 13 and a half years.

In contrast, right-wing extremists averaged 337 attacks per year in the decade after 9/11, causing a total of 254 fatalities, according to a study by Arie Perliger, a professor at the United States Military Academy’s Combating Terrorism Center. The toll has increased since the study was released in 2012.