In a never-before-released video, FBI agents posing as documentary filmmakers can be seen running an undercover operation to investigate a Nevada ranching family whose fight with the federal government sparked an armed uprising and rallied militias from around the country.

The undercover operation by “Longbow Productions” began shortly after the Bundy family and hundreds of supporters, many of them armed, forced government agents to surrender cattle they’d impounded from the family in 2014.

In audio and video recordings of the operation, an FBI agent going by the pseudonym “Charles Johnson” tries to find out the Bundy “family rank structure” and who planned the uprising in the desert town of Bunkerville.

He asks Ammon Bundy, who became the face of the family’s fight against the government, “Did you think you might have to take a life?” Bundy responded, “I never did once think I’d have to take a life.”

At another point, one of Ammon’s brothers, Ryan, asks the undercover crew: “I want to know if this is an interview or an interrogation.”

The footage is now part of a sweeping federal case against Ammon, Ryan, their father Cliven Bundy, and two others. The existence of the materials was confirmed in court filings, but its release has been blocked by a federal judge in order to protect the identities of the undercover agents.

FRONTLINE obtained video and audio recordings of the operation in the course of reporting for the film American Patriot: Inside the Armed Uprising Against the Federal Government, a months-long investigation of the Bundys’ confrontations with federal agents and the militia movement they helped inspire.

(In the clip above, FRONTLINE has concealed the agents’ identities and voices.)

Federal prosecutors declined to comment on the operation, as did the FBI.

In an interview from prison, Ammon said the Bundys were at first wary of Longbow and reluctant to participate. “We actually said no the first couple of times. We just didn’t feel comfortable … But he was persistent.”

Ultimately, Ammon agreed to participate, and convinced his family to as well. “I think about that the whole time my mom’s in there peeling potatoes for them, cooking for them, they’re plotting to destroy our family,” he told FRONTLINE.

The Bundys are scheduled to go on trial next month on multiple charges, including conspiracy and assaulting and threatening a federal agent.

Ammon Bundy’s attorney, Dan Hill, called the FBI operation troubling.

“They impersonated journalists so they could interrogate people the FBI fully intended on charging with serious crimes, without any lawyers present,” he said. “We should not have to fear that our government is infiltrating America’s sacred press and media institutions in order to try to gain prosecutorial advantages against its own people.”

After coming under criticism for this type of operation in the past, the FBI inspector general recommended that they be limited to circumstances approved at a high level within the bureau.

As part of the Longbow operation, the FBI also used its access to the Bundys to interview militia members who had been at the Bunkerville standoff. One of them, Greg Burleson, was part of a militia in Arizona.

While undercover cameras were running, the agents gave Burleson alcohol and asked him what the response would have been had the federal government crossed into a perimeter the militia had set up in Bunkerville. Burleson responded: “Dead bodies. Literally.”

The footage was used to help convict Burleson last month on eight charges, including threatening and assaulting a federal officer. He faces a minimum of 57 years in prison.

As the investigation was going on, Ammon Bundy travelled to Oregon, where in January 2016 he ended up staging an armed standoff — this time occupying the Malheur National Wildlife Refuge. The standoff ended in Bundy’s arrest, as well as in the death of one of the other occupation leaders — Robert LaVoy Finicum.

In October, Ammon Bundy was acquitted of conspiracy for his role in the Malheur showdown, as was his brother Ryan and five others. In a second trial, two more supporters were acquitted of conspiring to impede federal officers, but convicted of lesser charges.

Last month in Nevada, a judge declared a mistrial for four of Bundy’s co-defendants for their role in Bunkerville.

Soon after the Bunkerville standoff ended in April 2014, the undercover agent called the Bundy family to talk about filming at the ranch. In the audio recordings, Ammon Bundy comments that he cannot find much about Longbow Productions online.

“I just don’t keep a lot of stuff up there because it is not my product anymore,” the agent tells him. “That’s why I invested my money here because I don’t want it to go to the wrong hands.”

After some back and forth, Ammon says, “I think I’ve got what I wanted so I feel a lot more comfortable about it.”

Watch American Patriot: Inside the Armed Uprising Against the Federal Government on-air and online starting Tuesday, May 16 at 10 p.m. EST/9 p.m. CST on (check local PBS listings).

Correction: An earlier version of this story said that supporters of Ammon Bundy were convicted of misdemeanors. They were convicted of felonies.