U.S. lawmakers are heaping outrage and frustration on high-ranking federal bureaucrats who allowed thousands of powerful weapons to wind up in the arsenals of Mexican drug cartels.
Two of the guns were found at the scene of a Border Patrol agent's murder in Arizona last year.
The investigation involves an operation known as "Fast & Furious," conducted by the Bureau of Alcohol, Tobacco Firearms and Explosives.
The House Committee on Oversight and Government Reform, chaired by Congressman Darrell Issa of Vista, says top ATF officials ignored their own field agents' objections to letting guns 'walk' into Mexico so they could be tracked to their ultimate destinations.
As a result, says Issa (R-49th District), "approximately 2,000 AK-47s and derivatives, and some 50-caliber rifles and others and 10,000 or more rounds of live ammunition went into the arsenals of the Mexican drug lords."
According to investigators, two of the rifles traced to a suspect who'd made previous gun purchases monitored by ATF turned up where Border Patrol agent Brian Terry was fatally shot last December 15th.
"Likely a preventable tragedy" is how a House Oversight Committee report labeled the slaying.
Terry's family appeared Wednesday at a hearing before the House Oversight Committee.
"He (Terry) died not in Afghanistan or Iraq," said Robert Heyer, Terry's cousin, "but in the desert outside of Rio Rico, Arizona -- some 18 miles inside the (U.S.-Mexico) border."
ATF special agents testified that they were afraid their superiors' plans to track the weapons from U.S. gun stores to the cartels would backfire.
"Some of these guns could have been diverted with cartel drugs to New York, Baltimore, Oklahoma, or anywhere else in the country," said Peter Forcelli, group supervisor of ATF's Phoenix field division. "This was a catastrophic disaster."
The oversight committee released a series of emails it says demonstrate that ATF superiors were closely involved in "Fast & Furious."
They were so heavily redacted that Issa accused the agency of stonewalling Congress.
"Who authorized this program that was so felony stupid it got people killed?" he asked at one point.
"People are screaming that we've got to have a new assault weapons ban," Issa said later, in a satellite television interview. "Assault weapons are deliberately allowed to walk, and ultimately killing people on both sides of the border. We've got to get to the bottom of this. We've got to make sure that we don't let crooks have guns."
Issa added that he wants the oversight committee not just to focus on ATF, but to "go upstream a long way, to get to where the real culpability is."
ATF and Justice Department officials told the committee that they're doing their best to cooperate with the House investigation.
But they insisted that certain documents must continue to be withheld, for the sake of prosecuting defendants charged with Brian Terry's killing.