When a journalist for Univision asked President Obama last week why he hasn’t fired Attorney General Eric Holder over the “Fast and Furious” gun walking fiasco, the reporter, it turns out, had an inside scoop that added urgency to the question.

At 7 p.m. on Sunday, Univision says it’ll air a blockbuster investigation detailing the impact of the deeply flawed gunrunning investigation, which operated between October 2009 and January 2011.

The Spanish-language channel says the “Aqui y Ahora” program will expose the true deadly toll of a covert program in which US officials allowed more than 2,000 high-powered rifles to “walk” into the hands of violent Mexican cartels. Expecting American interest, Univision will caption the program in English.

In the US, “Fast and Furious” is most noted for its ties to the death of border patrol agent Brian Terry and for political fallout over the extent of involvement of the Obama administration, including Attorney General Holder. But in Mexico, the program may reignite furor over how a US government that had promised to try to halt the border gun traffic instead covertly contributed to it.

“Americans have been getting a lot of information about the possible cover-up in the Justice Department, the tragedy of Brian Terry getting killed, but what about the Mexicans?” says Miami-based Gerardo Reyes, Univision’s director of investigative reporting, in an interview Saturday with the Monitor.

“The sinister part of this, and I know it sounds very hard, is that the success of this operation depended in part on the fact that the guns were used in Mexico to kill,” says Mr. Reyes. “In order to reach the target of the operation, which was identifying the drug traffickers who were using the guns, [ATF agents] were waiting for the guns to be used. And how are guns used in Mexico? Killing people. I talked to an ATF agent who said there was no other way to explain it.”

ATF is the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

By cross referencing gun tracing data, Univision identified 57 weapons linked to murders and crimes in Mexico, and used that data to highlight “the face of the tragedy in Mexico,” says Mr. Reyes.

Reyes said the program will detail Fast and Furious ties to the massacre of 16 teenage boys and girls in Ciudad Juarez, the nation-shaking murder of Mario Gonzalez Rodriguez, the brother of the former Chihuahua attorney general, the extent to which the Mexican government knew about the program, and an interview with a drug trafficker who says he heard from colleagues that the US government was selling guns to the cartels.

The program comes two weeks after a long-awaited DOJ inspector general report was met with bipartisan approval as it chided the Justice Department and ATF for allowing Fast and Furious to ever happen, identified 14 people who should be held responsible, and suggested that the program was ultimately what Mr. Obama and Eric Holder originally said after Agent Terry’s murder: the product of an ill-advised ATF gambit in Phoenix, where employees later tried to cover up the fact that gunwalking was occurring.

The author of the report, Michael Horowitz, did note to the House Oversight Committee that a person who could have possibly connected Fast and Furious to the White House refused to be interviewed. Mr. Horowitz also faulted the Department of Justice for failing to pick up on what the program entailed, which could have been easily gleaned from wiretap applications sent for approval to the department in Washington.

Under the program, about 2,000 mostly AK-47s and some .50 caliber guns were allowed to be purchased by known straw buyers and “walk” without trace into Mexico. The gunwalking was at first denied by the Justice Department, which then had to concede that the government did indeed knowingly allow guns to cross the border.

Obama has called the program a mistake, but said it had an honorable intent: Under intense pressure to stymie tens of thousands of illegal guns flowing across the border, ATF, building on a smaller Bush-era program that cooperated with Mexican authorities, hoped agents could trace the guns beyond low-level straw buyers and to the highest levels of cartel. Some 40 people were indicted on charges brought using intelligence gleaned from Fast and Furious.

The question remains how far up in the Justice Department knowledge of the program went. Some Republicans suspect that it was a ploy brewed up at the highest levels, including Holder and Obama, to foment support for more domestic gun restrictions.

But Horowitz, the inspector general, found only blame at the lower reaches of the Justice Department, positing that the program was the product of a regional taskforce, not a national subterfuge intended by the administration to sway policy.

No matter how far up knowledge of Fast and Furious actually went, exposure of its true toll in Mexico will likely raise new questions about how such a fatally flawed operation could ever have happened.

In a press release for Sunday’s program, Univision says, “Univision News’ Investigative Unit was also able to identify additional guns that escaped the control of ATF agents and were used in different types of crimes throughout Mexico. Furthermore, some of these guns – none of which were reported by Congressional investigators – were put in the hands of drug traffickers in Honduras, Puerto Rico, and Colombia. A person familiar with the recent Congressional hearings called Univision’s findings ‘the holy grail’ that Congress had been searching for.”