WASHINGTON — On one end of the phone was a D.C. police lieutenant in charge of the intelligence unit. On the other, a man who called himself "Mason," purporting to be a top adviser to the white nationalist group Patriot Front, and its leader, Thomas Rousseau.

The veteran police supervisor, Shane Lamond, wanted to know when the group planned a return visit to the District, so police could prepare, and allow demonstrators to safely protest "without being attacked or hassled," he told the man on the other end of the line.

Mason pressed for intelligence on plots targeting his group. And he was interested in learning of police officers "sympathetic to what we're trying to do."

"These days, we like working with patriots, and it's hard for us to trust people that don't share those patriotic views," the man said. "Where do you stand on that question?"

Lamond laughed. "Unfortunately," he said, "I can't answer that question, for the simple fact that . . . I have to be objective. I can't express my personal feelings either way." Then he added, "I think if you look at just kind of the ideals and demographics of your group, and other groups, you all tend to be more favorable of law enforcement than other groups, I'll put it that way."

The man calling himself "Mason" told The Washington Post that he was not, in fact, affiliated with Patriot Front or its leader; he was an anti-racism activist posing as a member to out possible sympathizers. He said he recorded his dealings with Lamond, but shelved the exchanges when it appeared the police lieutenant didn't reveal secrets or admit to allegiances with the far-right.

But then in February, D.C.'s police chief put Lamond on leave amid an FBI investigation into his contacts with a different extremist group, the Proud Boys, and their leader, Henry "Enrique" Tarrio. The activist revisited his conversations with the purported Patriot Front member.

Mason provided his exchanges with Lamond to The Washington Post after Lamond's name publicly surfaced in the investigation of his contacts with the Proud Boys. He did so on the condition of anonymity, saying he might face retaliation from the neo-Nazi groups which he seeks to infiltrate, but gave The Post his real name. The materials he provided include email and Twitter direct message exchanges, as well as a recording of a phone call.

The interactions, which began in the days after the Patriot Front marched in the District in February 2020, provide rare insight into a police officer's interactions with someone suspected of being tied to a white nationalist group.

Lamond's attorney, Mark E. Schamel, said the texts, emails and audio recording appear authentic. The lawyer declined to comment further, as did Lamond. At first, the activist said he pretended to be Rousseau himself; he later switched personas, pretending to be one of Rousseau's aides.

Numerous attempts to reach Rousseau and representatives of the Patriot Front were not successful.

The recordings show a police officer trying to cultivate a relationship, and at times appearing friendly to a racist group. But experts say it is hard to assess whether they show Lamond crossing a line and getting too close with extremists - or simply working sources for information that he could use to keep people safe. Some of the contacts seem entirely legitimate, and the activist himself could face criticism for spurring police to focus efforts on him.

Mason and Lamond were in contact for months spanning two tumultuous periods in the District and for the nation - the social unrest over policing in the summer of 2020, and the attack on the Capitol in 2021. During nightly demonstrations over the Minneapolis police killing of George Floyd, officers arrested hundreds, as they confronted looting and fires downtown, and engaged in sometimes violent clashes with protesters. Later in the year, marches led by the Proud Boys produced street brawls, stabbings and more destruction.

Police intelligence officials were under pressure to learn of demonstrators' intentions, so they could try to head off possible violence.

In the wake of Lamond's suspension, his wife came to his defense in an internet post on the Christian crowdsourcing site GiveSendGo soliciting money for his defense, saying Lamond's job was to gather information on those who might cause harm in the city. As of Sept. 1, the site shows $8,042 had been raised.

"Help DC Officer suspended for doing his job," says one of the posts. Lamond's wife argued her husband kept "conflicting parties separate," and she accused authorities of "attempting to ruin a good police officer's life for doing his job."

The nature and scope of the FBI investigation involving Lamond's alleged contacts remains unknown, but D.C. Democratic Mayor Muriel Bowser said in February the inquiry is in part about "investigations involving January 6."

Tarrio and others are charged with seditious conspiracy in the Jan. 6, 2021, riot at the Capitol. Those charges are among the most serious filed by federal prosecutors in the sprawling criminal investigation of the riot.

Experts said some of Lamond's conduct was especially concerning if he did not clear the dealings with supervisors.

Lamond first reached out to the activist's fake Twitter account — named in a way it appeared to be Rousseau's, though it was set up and monitored by the activist — on Feb. 20, 2020, according to documents shared with The Post. About 100 masked members of the Patriot Front had marched 12 days earlier along the National Mall.

Mason said he was trolling the internet, hoping to draw out Patriot Front members and expose sympathizers to discredit followers. Rousseau has little to no social media presence and operates in areas of the internet not easily accessible to casual users. At one point in a phone conversation, Lamond wondered aloud if he was being duped, and if the person he was talking to might be posing as a Patriot Front officer.

Mason said he wasn't searching for a police officer, and the contacts from Lamond were "a happy accident."

"Hey Thomas, it's Shane Lamond with the D.C. police," the lieutenant wrote in a direct message on Twitter. Lamond noted he had given Rousseau his business card at the earlier march, and he wanted to know if the Patriot Front planned to return for Memorial Day.

"We won't interfere with you or try to stop you from conducting your demo, but if I have a heads up ahead of time I can prevent all the craziness from the last time like the helicopter and the 50 million cops," Lamond told the activist, who was then pretending to be Rousseau himself.

Megan Squire, a senior fellow at the Southern Poverty Law Center, described Rousseau as "extremely paranoid" about his organization being infiltrated, doxed or exposed, to the point of sacrificing outreach and membership for security.

She said Lamond's following an impostor online was, "frustrating to watch," because the activity could "suck energy from other things police intelligence units need to be doing."

In their conversations, Lamond assured the activist, "Any information you provide me would be kept strictly confidential; it would be kept very quiet to a few MPD members for planning purposes." And he said he "took a big risk" reaching out to the group.

As the discussion continued, Lamond messaged: "If you prefer to call me so nothing is in writing that's cool."

Shane Sims, a former FBI agent and CEO of the cybersecurity firm Kivu Consulting, who reviewed the exchanges between Lamond and Mason for The Washington Post, noted several possible "red flags" in the conversations.

Those include Lamond agreeing to take conversations offline, and his suggestion he would "collaborate" with Mason at a rally.

"Hi Thomas, I never heard from you. With everything that is going on in DC and across the country there isn't a better time to communicate/collaborate," Lamond wrote in a message.

Sims said those phrases could pique the interest of federal law enforcement. But Sims also said it is important to know if Lamond followed proper protocols during his interactions with the person he thought was the Patriot Front leader or its representative. He said best practice is for intel officers to pair with a colleague and document every contact to ensure nothing is misconstrued. He said that "being untruthful is OK" to earn someone's trust.

"Ultimately, this comes down to whether or not he was documenting things properly, in accordance with department's policies and procedures," Sims said. "If not, the red flags become a deeper state of red."

Keith Taylor, a former New York City police supervisor and assistant commissioner for that city's corrections department, overseeing gang intelligence, said it is important for law enforcement agencies to forge relationships with representatives of groups, regardless of their politics or ideologies.

But Taylor, now an adjunct assistant professor at John Jay College of Criminal Justice, said developing informants requires close supervision and monitoring.

"Police officers are not allowed to act as their own entities," Taylor said.

A D.C. police spokesman declined to comment on the investigation into Lamond's contact with the Proud Boys — or on his dealings with Mason — other than to say he remains on administrative leave. The U.S. attorney's office in D.C. and the FBI declined to comment.

Federal prosecutors in the criminal case against Tarrio turned over to Tarrio's defense lawyers chats between Lamond and the Proud Boys leader, as well as summaries of interviews with police officials "relating to contacts between Tarrio and Lamond."

Nayib Hassan, an attorney for Tarrio, declined to provide those communications to The Post, saying they have been "classified as highly sensitive." He said that Tarrio and Lamond "had a professional relationship" that was "limited to necessary information regarding when Proud Boy rallies would occur and their location during the rally."

In a recent court filing, Hassan described Lamond as the police department's "point of contact" with Tarrio, and noted the lieutenant and others were concerned that the Proud Boys planned to eschew wearing their signature colors on Jan. 6 so they could not easily be identified.

Tarrio was arrested two days before the riot on charges that he burned a Black Lives Matter banner stolen from a historic African American D.C. church during a violent Proud Boys march the previous month. He was set free the next day to await trial, but barred from the District, keeping him out of the nation's capital on Jan. 6.

As he left the city, he met in an underground parking garage with Stewart Rhodes, the founder of the extremist group Oath Keepers, and others. In a 22-minute video that captured part of that meeting, he told a participant that he knew of his pending arrest as he flew into a D.C.-area airport.

"In the air is when I knew they signed the warrant," Tarrio said, without explaining how or by whom. He added, "They texted me from the air."

The day it was announced that Lamond had been placed on leave, Tarrio told The Washington Post that he had talked often with the lieutenant before and during marches in D.C., describing those contacts as professional. He said Lamond would tell him the location of counterdemonstrators. Tarrio said that was so his group could avoid conflict, though after one violent night of demonstrations, police accused the Proud Boys of roaming the city looking for and instigating fights, targeting people they believed to be antifascists.

In a recorded phone conversation with Mason, Lamond said his primary objective was to get a heads up when Patriot Front visited the District, to "make sure there are no counter groups interfering with your right to demonstrate."

On Jan. 29, 2021 - about three weeks after supporters of President Donald Trump stormed the U.S. Capitol - the Patriot Front came to the District and marched. D.C. police said at the time they were "aware previously that demonstrations were to take place." But that information apparently didn't come from Lamond.

The lieutenant fired off email to the person he thought was Rousseau. "Maaan, I thought we were forging a partnership to share Intel but you didn't give me a heads up you were coming! I was out on foot with you all but I couldn't get close enough to say hi. At least there were no issues."

Five days later, the activist apologized for the "breach of trust" but said the events of Jan. 6 had changed everything. "My guys and I thought it would be a bad idea to try to coordinate anything with LE in the expectation that any response would be pretty heavy handed," the activist wrote back.