(CNN) -- Federal authorities unsealed Monday an indictment charging five men in the death of U.S. Border Patrol Agent Brian Terry and offering up to $1 million for information leading to the arrest of the four men still at large.
The investigation into the December 2010 killing revealed the existence of a botched federal operation that had sought to investigate U.S.-Mexican arms trafficking and led to the historic vote by the House of Representatives that found U.S. Attorney General Eric Holder in contempt of Congress.
The indictment charges Manuel Osorio-Arellanes, Jesus Rosario Favela-Astorga, Ivan Soto-Barraza, Heraclio Osorio-Arellanes and Lionel Portillo-Meza with first-degree murder, second-degree murder, conspiracy to interfere with commerce by robbery, attempted interference with commerce by robbery, carrying and using a firearm during a crime of violence, assault on a federal officer and possession of a firearm by a prohibited person.
A sixth defendant, Rito Osorio-Arellanes, is charged solely with conspiracy to interfere with commerce by robbery.
A federal grand jury in the District of Arizona handed up the 11-count indictment November 7. It alleges that, on December 14, 2010, five of the defendants (Manuel Osorio-Arellanes, Jesus Rosario Favela-Astorga, Ivan Soto-Barraza, Heraclio Osorio-Arellanes and Lionel Portillo-Meza) were involved in a firefight with Border Patrol agents during which Terry was fatally shot.
The indictment says the defendants had entered the United States illegally from Mexico in order to rob drug traffickers of marijuana. Terry was fatally shot when he and other members of a Border Patrol tactical unit tried to apprehend the men, officials said.
Laura E. Duffy, U.S. attorney for the Southern District of California, noted to reporters in Tucson, Arizona, that covert efforts had not resulted in any arrests, and said officials decided it was in the best interests of the investigation to unseal the case and enlist the assistance of the public in the United States and Mexico.
Toward that end, James L. Turgal Jr., FBI special agent in charge, Phoenix Division, said the FBI was offering up to $250,000 per fugitive for information leading to their arrest.
The incident occurred in Rio Rico, Arizona, a remote area commonly used by people smuggling drugs into the country on foot, she said. It is about 10 miles north of the border.
That night, four members of the Border Patrol team were on a steep hill above a wash; two other team members were in a nearby observation post from which they could monitor foot traffic and relay radio communications, Duffy said.
Soon after 11 p.m., a ground sensor alerted the team to the presence of people on foot in the area; within a few minutes agents saw five armed men walking toward the agents, she said.
"As the armed group passed through the wash below, the agents announced their presence; several of the armed individuals turned with weapons raised," she said. The agents fired nonlethal bean-bag rounds at the subjects, who responded with gunfire, she said. A single bullet struck Terry, who died at the scene.
Four of the five suspects fled; the fifth, Manuel Osorio-Arellans, was wounded and taken into custody.
Two days before, on December 12, Border Patrol agents had arrested a sixth man, Rito Osorio-Arellanes, who was to have been part of the group, Duffy said. He was charged with conspiracy to commit robbery.
He is Manuel Osorio-Arellanes' brother; both men are in custody in Arizona, Duffy said. "The other four are believed to be at large in Mexico." If they are arrested, U.S. officials will seek their extradition, she said.
The case has attracted attention because of its link to Operation Fast and Furious. Launched by the Bureau of Alcohol, Tobacco, Firearms and Explosives, the operation was intended to track weapons purchases by Mexican drug cartels.
However, the operation lost track of more than 1,000 firearms that the agency had allowed straw buyers to carry across the border, and two of the lost weapons turned up at the scene of Terry's killing.
Duffy alluded to the controversy that has swirled around the case, which has provided ample fodder for AM-radio talk-show hosts, noting that "there are almost unprecedented atmospherics that have surrounded this case."
She would not say whether the bullet that killed Terry came from one of the guns involved in the botched program.
But, she added, "I want the Terry family and members of the U.S. Border Patrol to know that those atmospherics have not distracted the efforts of this prosecution team."
Congress voted June 28 to hold Holder in contempt for refusing to hand over documents related to the program.
Republicans said that was because he was not fully compliant with a House subpoena requesting the documents; Democrats and the Justice Department countered that the documents withheld were internal deliberations that have, by tradition, been kept private during past administrations of both parties.
"Agent Terry served his country honorably and made the ultimate sacrifice in trying to protect it from harm, and we will stop at nothing to bring those responsible for his murder to justice," Holder said.
In a statement, Terry's family members thanked Duffy and the Mexican government for their efforts in the investigation and reiterated their call for Holder to comply with the request for documents related to the case.
"Agent Terry died as a hero protecting this country; he and his family rightly deserve a full and thorough explanation of how Operation Fast and Furious came to be," said Terry family attorney Patrick McGroder in the statement from the family.
Rep. Jason Chaffetz said the indictments should have been unsealed long ago. "It's too bad that it didn't happen 14 months ago," said the Republican from Utah, who is on the House Oversight and Government Reform Committee, in a telephone interview.
He accused the Justice Department of having "not taken this seriously."
CNN's Carol Cratty contributed to this report