When Leon County Sheriff’s Deputies Christopher Smith and Colin Wulfekuhl responded to a call about a house fire in Tallahassee last Saturday, they were greeted by the burning home’s occupant, 53-year-old Curtis Wade Holley, brandishing a .40 caliber handgun. It soon became clear that the flames were no accident, as Holley proceeded to initiate a shootout with the first responders, managing to shoot and kill Smith before being gunned down by another officer.

At a press conference the following day, Sheriff’s Office Spokesman Lt. James McQuaig told reporters that the incident was clearly a planned attack by Holley, who lured first responders by setting his house on fire and waiting for it to become completely engulfed in flames before asking a next door neighbor to call 911.

“We have information that we have received that this person was anti-government, was anti-establishment and had discussed at some point in time planning to harm law enforcement,” McQuaig said. “It was a 100 percent ambush. This guy had a plan and he put this plan into action.”

Though the specifics of Holley’s anti-government beliefs and previous threats have not been reported, some bloggers have suggested that Holley identified with the burgeoning sovereign citizen movement who, in addition to their other beliefs, completely reject the authority of law enforcement.

Despite or, perhaps, because of its loose organization, the sovereign citizen movement has become a major concern for local, state, and federal law enforcement. On the most basic level, sovereign citizens don’t believe in taxes, government, or the authority of any official above a county sheriff. They are known for perpetuating so-called “paper terrorism,” filing hundreds of pages of nonsensical paperwork to local courts in an effort to avoid something as simple as a parking ticket, or submitting fake property liens or tax forms designed to destroy an enemy’s credit or get them audited.

Sovereign citizens are not explicitly violent, but over the past few years the number of lone wolf attacks on law enforcement by followers of the movement, have prompted the FBI to consider sovereign citizens a major domestic terrorism threat. This summer, the University of Maryland’s National Consortium for the Study of Terrorism and Responses to Terrorism released the results of a study finding sovereign citizens are perceived to be the single greatest threat to law enforcement, above Islamist extremists and patriot or militia groups.

It wasn’t more than five years ago, however, that sovereign citizens were flying completely under the FBI and other law enforcement’s radar. That changed on May 20, 2010 when Brandon Paudert and Bill Evans, two police officers in West Memphis, Arkansas pulled over a suspicious white minivan with strange-looking Ohio license plates and were shot and killed by the van’s 16-year-old, AK-47-wielding passenger. The shooter, Joseph Kane, and his father Jerry, who were eventually killed in a shootout with police after leaving Paudert and Evans at the scene, were sovereign citizens.

Brandon Paudert’s father, Bob, was the West Memphis chief of police at the time. He tried desperately to find some information on the sovereign citizens, calling police departments across the country, but no one knew who they were. This lack of information prompted Paudert to do his own research and he began lecturing law enforcement groups on how to identify sovereign citizens and stop them before it’s too late. A little more than a year after his son was killed by sovereign citizens, Paudert decided to retire from his 44-year law enforcement career and dedicate his time to travelling across the country, educating police on the potential dangers of this fringe movement.

Often, the most common opportunity for police officers to encounter a sovereign citizen is during a traffic stop. So one of the most important things Paudert teaches police officers is to be able to identify the bogus paperwork a sovereign citizen will present when asked for license and state registration. By virtue of their rejection of government and law enforcement, sovereign citizens generally do not have drivers licenses or state registration for their cars, instead carrying some sort of a driver’s card that confuses police and allows the sovereign citizen to take control of a traffic stop. By simply being able to recognize these driver’s cards, Paudert says, cops can quickly identify when they’ve pulled over a sovereign citizen and should immediately call for backup.

“Every state has sovereign citizens. Every state.” Paudert told The Daily Beast. “They tend to like rural areas, in the woods, isolated, because many of the sovereigns just want to be left alone. They don’t want contact with the government.”

In fact, Paudert said, while many are not violent, he has found that the more interactions a sovereign has with law enforcement, the more likely they are to snap. He points to the Kanes as an example, noting that Jerry Kane had had several encounters with police prior to the May 2010 shooting, and he wasn’t going to take another one.

“He knew 30 days in advance he was going to kill the next time he had a traffic stop,” Paudert said. “ He knew that, we didn’t We didn’t even know what sovereigns were. We were at a total disadvantage.”

Traffic stops may be the most common setting for an interaction between police and sovereign citizens, but such animosity toward law enforcement has also driven more elaborate attacks, akin to the trap apparently set by Curtis Wade Holley. In January, for example, an Ohio sovereign named Mark Kulis wired his house with explosives that would be discovered by sheriff’s deputies when they came to deliver an eviction notice. Other sovereign attacks on police in recent years include a 2012 ambush on Louisiana sheriff’s deputies patrolling a trailer park outside New Orleans, which left two officers dead and two others wounded; and a shootout between a 60-year-old sovereign citizen Brent Douglas Cole and a Bureau of Land Management ranger and California Highway Patrol officer who’d approached Cole’s northern California campsite this summer. No one was killed in this incident, but both law enforcement agents as well as Cole were wounded.

The Southern Poverty Law Center, which tracks hate groups, extremist movements and individuals throughout the U.S., was not aware of Curtis Wade Holley prior to last weekend’s shootout. But the group has been paying close attention to the sovereign citizens for a while. Following the 2010 shooting of officers Brandon Paudert and Bill Evans in West Memphis, the SPLC put out a training video on the sovereign citizen threat. Since then, they’ve worked with Bob Paudert and other law enforcement groups across the country to educate police on how to protect themselves against such potentially violent people.

Paudert is sure to acknowledge that sovereign citizens have the same rights as all Americans and that they are not all dangerous. He also notes that it a growing movement, attracting people from all over the country and all over the professional spectrum, from out-of-work truck drivers to law enforcement officers, TSA agents, and business professionals, most initially attracted by the opposition to taxes and federal government power.

“I agree with a lot of things they have to say,” Paudert admitted. “I think taxes are too high and the federal government is too big. But I pay my taxes and I don’t kill police officers. They are willing to kill and be killed for their beliefs.”