D.C. Police Sgt. Dale Sutherland’s high-tech headquarters in a stylish Northeast rowhouse welcomed some of the city’s most notorious gun-runners and drug dealers.

Sutherland made deals for revolvers, shotguns, ammunition, crack cocaine and heroin from black leather couches. His suppliers kept coming back, authorities say. Then, in June, one offered Sutherland hand grenades and a rocket launcher, and he had to act quickly.

What the dealers didn’t know at the time: The house, dressed up as a recording studio, was wired by the FBI, and Sutherland — and all his buyers — were undercover officers. When an officer listening in on a telephone conversation overheard plans to rob them, a year-long sting operation began to wind down.

Those encounters, described in court papers, were among the many that occurred during the sting, which was unveiled Monday. Authorities say officers posing as gangsters, crooked businessmen and bodyguards helped snag $7.2 million in cocaine, PCP and other drugs, buy and capture 161 weapons, and make 70 arrests.

Authorities said it was one of their most important weapons investigations in recent history.

“Had those drugs and guns made it to our streets, the consequences would be devastating,” D.C. Police Chief Cathy L. Lanier said Monday at a news conference.

The face of the the sting operation was Sutherland, a veteran of undercover work. Posing as Manic Enterprises impresario Richie Valdez, head of an international string of recording studios, Sutherland convinced criminals that he was one of them, and that he wasn’t afraid to rob banks and drug dealers to boost his trade in guns and drugs. But Valdez’s associates were D.C. police narcotics investigators.

Police and agents from the FBI; Bureau of Alcohol, Tobacco, Firearms and Explosives; Drug Enforcement Administration; and Immigration and Customs Enforcement uncovered connections to a Mexican drug cartel and out-of-area gun traders that led to federal investigations in a half-dozen states and a murder case in El Salvador.

The investigation offered a rare opportunity to fight violent crime by attacking the sources of the dangerous weapons that flow into the city, authorities said.

“We concentrated on some higher-value targets,” ATF Assistant Special Agent in Charge Richard Marianos said Monday.

“They had real connections to real gun traffickers,” said Sutherland in an interview. “It is unusual to get that many guys that have a ‘connect’ where they can get guns steady. . . . We know criminals have this kind of stuff on the street, but we don’t get to recover it very often.”

The salesman who promised rocket launchers was Chris Washington, according to court papers that say he also sold officers drugs. His case is pending.

Another man, James Deale, admitted to selling undercover officers AR-15 assault rifles, but he also sold made-to-fit handgun silencers, which police said are rarely found on the streets.

“I never thought guys could get guns as fast as those guys can get guns,” Officer Kief Green, who posed as Valdez’s bodyguard, said in an interview. “Amazing.”

Lanier said operations such as these help the department combat gun crime and keep homicides down.

“What they did here was prevention,” she said Monday. “The street-level enforcement is important, but it’s only marginally effective unless you go after the source.”

The operation differed from some other recent undercover projects in the District. In 2009, Lanier and federal investigators revealed a sting run out of a phony auto body shop during which police sought to pull guns and drugs off the streets quickly.

“This time it was more of a conversation: ‘Give me your résumé of what you do,’ ” Lt. Eugene Bentley, who supervised both operations, said in an interview. “This was totally different.”

Authorities declined to discuss many of the operation’s tactical details, but interviews and court documents provided a partial illustration of their methods.

Once inside the Northeast house’s iron gate, visitors found gleaming hardwood floors and a flat-screen television in the entryway. Upstairs, a Plexiglas window divided a studio built in a converted bedroom from a sound system, couches, a mini-fridge and a bar.

The furniture was purchased at the Salvation Army; the floors were buffed by Green. Police said some targets tried to book studio time but were rebuffed by Sutherland.

The hidden audio and video equipment recorded hundreds of hours of meetings and deals struck by Sutherland, detective Frank Then — in the role of business associate — and others posing as girlfriends and bodyguards.

Confidential informants lured targets to the studio, courting them with food, beer and high-end tequila.

Police worked to set up bigger deals not only in the Washington area but also in New York, North Carolina, Georgia and West Virginia.

A November 2010 meeting led to the eventual arrest of eight men authorities said were connected to the Mexican drug cartel “La Familia.” One of them allegedly claimed to run local drug operations for the gang, which wanted to establish a methamphetamine market in the District. In October, six pleaded guilty to federal drug charges in connection with the case.

This spring, detectives met with six other men they say needed guns, bulletproof vests, vehicles and a driver to rob a Pennsylvania bank, authorities said. They were professionals, investigators say — organized, determined and willing to face danger for the right price.

“They didn’t even drink alcohol,” Sgt. Deryl Johnson said in an interview. “These guys were just cold.”

That sometimes meant danger. On one occasion, police say, a suspected MS-13 gang member pulled out a silver pistol, waving it drunkenly around the room. He kissed it, called it his “baby” and bragged about using it in robberies, police said.

Officers offered to buy it from him, but the man refused. Officers persuaded him to put it back in his pocket, then radioed other officers to arrest him after he left the studio.

In June, police said, one target accidentally dialed the phone of an officer who was posing as “Tony Blanco.” When the officer picked up, he overheard men discussing a plan to storm the studio, guns blazing.

Investigators immediately began their own preparations. On June 20, a surveillance team overheard men finalizing their plot at a Northeast hamburger shop. Police were primed to stop them before they started, but the attack never came. The men eventually were arrested in another part of the city.

In November, investigators who worked on the operation held a party where each one received a plaque in the shape of a gold record marked with the sting’s name: “Operation Manic Enterprises.”

At Monday’s news conference, Lanier called the team “heroes.” Marianos recalled the city’s two latest high-profile undercover stings: “Two years ago, we made a commitment that this wouldn’t be a one-trick pony,” he said. “We are going to make moves against predators in this city.”