Room 2154 of the Rayburn House Office Building, the scene of many heated partisan arguments, was packed but solemn, as Robert Heyer spoke about his cousin, slain Border Patrol agent Brian A. Terry.

Seated with Terry’s mother and sister, Heyer told the House Oversight and Government Reform Committee hearing about a federal law enforcement officer whose killing has been linked to a failed gun-trafficking operation by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

“It was just 10 days before Christmas last year when our family received the devastating news — Brian had been shot and killed while engaged in a firefight with a group of individuals seeking to do harm to Americans citizens and others . . .” Heyer said.

“The telephone call in the middle of the night,” he continued, delivered word that Terry died “in the desert outside of Rio Rico, Arizona, some 18 miles inside of the U.S.-Mexican border. His killers were not Taliban insurgents or al-Qaeda fighters but a small group of Mexican drug cartel bandits heavily armed with AK-47 assault rifles.”

Two of the AK-47s recovered at the scene — though apparently not the weapon used on Terry — were purchased under the eyes of an ATF operation called “Fast and Furious.” Its purpose was to track guns that could end up in the hands of the cartel bandits.

But the operation went south faster than some of the guns being tracked.

Working with legitimate gun dealers, ATF agents would learn about illegal gun sales. The idea, Assistant Attorney General Ronald Weich told the hearing, was “dismantling a significant transnational gun-trafficking enterprise and the network of those who support the enterprise’s criminal efforts, an investigation which has already led to the indictment of 20 defendants.”

The agents on the ground, however, tell a different story, one of frustration and anger as they were repeatedly ordered not to stop people suspected of holding the illegal arms. They knew they would see those guns again, when it was too late — as was case with the AK-47s at Terry’s killing.

With a startling degree of frankness for federal employees discussing their agency, three ATF agents described the failure of Fast and Furious. They named supervisors whose orders contradicted what the agents thought was their sworn duty — capture the bad guys with the guns. The bosses said the agents didn’t understand the bigger picture.

“Rather than conduct any enforcement actions, we took notes, we recorded observations, we tracked movements of these individuals for a short time after their purchases, but nothing more,” Special Agent John Dodson said. “Knowing all the while, just days after these purchases, the guns that we saw these individuals buy would begin turning up at crime scenes in the United States and Mexico, we still did nothing. . . . Allowing loads of weapons that we knew to be destined for criminals — this was the plan. It was so mandated.”

A statement by the Justice Department said that officials take the allegations seriously. “The department has also made clear to law enforcement agencies and prosecutors working along the Southwest Border that under no circumstances should guns be allowed to cross the border into Mexico.”

But, at a minimum, some guns apparently were allowed to get into the hands of criminals in the United States, including those involved in Terry’s slaying.

“There have been grave mistakes in this case,” supervisory Special Agent Peter J. Forcelli told the panel. “The committee, the American people and the family of slain U.S. Border Patrol Agent Brian Terry deserve answers.”

The agents appeared under what people on Capitol Hill call a “friendly subpoena,” which is served on witnesses who want to testify but need a subpoena to protect them from being fired. Weich assured the committee that no action would be taken against the agents because of their testimony.

Senior Special Agent Olindo James Casa said, “It has become common practice for ATF supervisors to retaliate against employees that do not blindly tow the company line, no matter the consequences.”

Forcelli, in an interview after the hearing, said he had received “nothing but phenomenal support” from his superiors. “They’ve been extremely supportive and said ‘go and tell the truth.’”

The most poignant moment in the hearing, held by committee Chairman Darrell Issa (R-Calif.), came when Heyer read a poem that Terry wrote during training as a member of BORTAC, the Border Patrol’s elite tactical unit:

“. . . I’m willing to die if necessary. I do not fear death for I have been close enough to it on enough occasions that it no longer concerns me.

“But I do fear the loss of my honor and would rather die fighting than to have it said that I was without courage.”