Officials at the Department of Justice are in "panic mode," according to multiple sources, as word spreads that congressional testimony next week will paint a bleak and humiliating picture of Operation Fast and Furious, the botched undercover operation that left a trail of blood from Mexico to Washington, D.C.

The operation was supposed to stem the flow of weapons from the U.S. to Mexico by allowing so-called straw buyers to purchase guns legally in the U.S. and later sell them in Mexico, usually to drug cartels.

Instead, ATF documents show that the Bureau of Alcohol Tobacco and Firearms knowingly and deliberately flooded Mexico with assault rifles. Their intent was to expose the entire smuggling organization, from top to bottom, but the operation spun out of control and supervisors refused pleas from field agents to stop it.

Only after Border Patrol Agent Brian Terry died did ATF Agent John Dodson blow the whistle and expose the scandal.

"What people don't understand is how long we will be dealing with this," Dodson told Fox News back in March. "Those guns are gone. You can't just give the order and get them back. There is no telling how many crimes will be committed before we retrieve them."

But now the casualties are coming in.

Mexican officials estimate 150 of their people have been shot by Fast and Furious guns. Police have recovered roughly 700 guns at crime scenes, 250 in the U.S. and the rest in Mexico, including five AK-47s found at a cartel warehouse in Juarez last month.

A high-powered sniper rifle was used to shoot down a Mexican military helicopter. Two other Romanian-made AK-47s were found in a shoot-out that left 11 dead in the state of Jalisco three weeks ago.

The guns were traced to the Lone Wolf Gun Store in Glendale, Ariz., and were sold only after the store employees were told to do so by the ATF.

It is illegal to buy a gun for anyone but yourself. However, ATF's own documents show it allowed just 15 men to buy 1,725 guns, and 1,318 of those were after the purchasers officially became targets of investigation.

Arizona gun store owners say they were explicitly told by the ATF to sell the guns, sometimes 20, 30, even up to 40 in a single day to single person.

And those orders, from at least one ATF case agent, are on audio recording.

"We would say, 'Do you (the ATF) want us to stop selling, is there something we should do here?'" Brad DeSayes, owner of J&G Gun Sales in Prescott, said. "And they would say, 'No, no, no, keep selling - just tell us after the fact.'"

Rep. Darrell Issa, chairman of the House Committee on Oversight and Government Reform, holds a hearing Wednesday into Operation Fast and Furious.

The hearing is billed as "Reckless Decisions, Tragic Outcomes," and the following are among the details expected in testimony:

- The ATF allowed and encouraged five Arizona gun store owners to sell some 1,800 weapons to buyers known to them as gun smugglers.

- It installed cameras inside the gun stores to record purchases made by those smugglers.

- It hid GPS trackers inside gun stocks and watched the weapons go south on computer screens.

- It obtained surveillance video from parking lots and helicopters showing straw buyers transferring their guns from one car to another.

- It learned guns sold in Phoenix were recovered only when Mexico police requested "trace data," which is obtained from their serial number.

The first witness in Wednesday's hearing is Sen. Charles Grassley, who will describe what his investigative team learned from four months of interviews and thousands of documents. He will be followed by three members of Brian Terry's family, three ATF agents and Assistant Attorney General Ronald Weich, who only months ago insisted the agency did not let guns go south to Mexico, a claim contradicted by field agents in Group 7, the actual agents who ran the operation in Phoenix.