DENVER – One of the nation’s fastest-growing motorcycle clubs is composed largely of military, police officers and prison guards. It also embraces the regalia and traditions of outlaw biker gangs – a choice that has provoked deadly clashes with other groups.

The Iron Order club insists it is a law-abiding, charitable brotherhood of family men who just like to ride. But experts say its members are increasingly becoming entangled in violence with other biker groups, blurring the line between professionals who are sworn to uphold the law and a biker culture with a long history of criminal activity.

“It’s almost like they are playing dress-up on the weekend and acting out what their perception of an outlaw gang is,” said David Devereaux, a spokesman for the National Council of Clubs, which represents hundreds of motorcycle groups. “They create aggressive situations with other motorcycle clubs in opposition to the culture.”

The latest skirmish happened Saturday, when the Iron Order and the Mongols motorcycle club clashed in a brawl that left a Mongols member dead.

The two groups blame each other for inciting the violence at the Colorado Motorcycle Expo, a gathering of biker groups from across the country. Police are not sure what set off the fight, which left seven other people shot, stabbed or beaten. More than one person fired a weapon during the melee, including a Colorado Department of Corrections officer who wore patches that clearly identified him as a member of the Iron Order.

No one has been arrested, adding to the frustration of other groups that complain Iron Order members pick fights, then use their law enforcement connections to avoid prosecution.

It’s not uncommon for law enforcement to join motorcycle clubs. Some groups exist exclusively for police, such as the Blue Knights, which has almost 20,000 members and performs community services year-round. A source of friction is that the Iron Order consists of both law enforcement and other professions, and it adopts emblems more common to well-established gangs, according to experts.

The Iron Order says its members have lawfully defended themselves during confrontations provoked by other groups that feel threatened by the club’s rapid growth and its open disregard for time-honored rules of motorcycle culture.

An Iron Order recruit fatally shot a member of the Black Pistons motorcycle club during a June 2014 fight outside a bar in Jacksonville Beach, Florida. The shooter said members of the other group attacked him and broke his nose. Three people were shot in a February 2015 gunbattle with bikers affiliated with the Bandidos gang. A fourth person was hit over the head with a baton.

A few years earlier, in 2011, an Iron Order member was stabbed by another gang member in South Carolina. And a 2014 melee at a Baltimore strip club involved Iron Order members who were attacked by riders from the Iron Horsemen group who wielded flashlights, hammers, bats and knives.

Accounts of some of those episodes were contained in a 2014 report from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives describing the involvement of the military in motorcycle gangs. The report described Iron Order as one of the nation’s fastest-growing clubs that continues to expand into territories normally controlled by well-established outlaw gangs despite the violence.

The ATF says the club “infuriated” the most notorious motorcycle gangs, such as the Hells Angels and Pagans, by wearing a three-piece patch arrangement with a crescent-shaped bottom patch bearing the name of a state. The bottom “rocker” historically belonged to outlaw gangs, called “one-percenters.” But Iron Order never sought their permission to use it and took colors already claimed by other clubs, said John C. Whitfield, an Iron Order attorney and a member himself.

The Iron Order group formed in 2004, seeking the mystique of outlaw gangs without the crime, he said. The founders liked the motorcycle fellowship, which reminded them of the camaraderie of a military unit or a police department.

“We wanted to kind of change the dynamics of the motorcycle world,” Whitfield said. A lot of members like the three-piece patch for its “cool factor,” he said. “There’s a little bit of danger that kicks in, and it kind of makes these weekend warriors feel like they are a little bit dangerous. But we’re not.”

There has been “a ton of pushback” from other groups as a result, Whitfield said.

Other police clubs also wear three-piece patches but have no trouble with other groups, said Stephen Stubbs, an attorney for the Mongols.

“It’s not about the patches. It’s about Iron Order living out its ‘Sons of Anarchy’ fantasy, starting fights and causing trouble,” Stubbs said, referring to a cable television show about an outlaw motorcycle club.

The Iron Order group usually goes out of its way to avoid crime, even requiring its members to have concealed-carry weapons permits as a way to vet for convicted felons, said Steve Cook, executive director of the Midwest Outlaw Motorcycle Gang Investigators Association, which offers training for police agencies.

Iron Order members typically cooperate with law enforcement, while their outlaw counterparts swear against doing so, he said.