By JACQUES BILLEAUD
PHOENIX (AP) -- A Mexican man pleaded guilty in Tucson federal court Tuesday to the killing of a U.S. Border Patrol agent during a 2010 firefight near the Arizona-Mexico border, marking the first conviction in the agent's death.
Prosecutors agreed not to seek the death penalty against Manuel Osorio-Arellanes, who could face life in prison for his first-degree murder plea in the death of Border Patrol Agent Brian Terry.
The deadly shooting has prompted congressional probes of a bungled government gun-smuggling investigation known as "Operation Fast and Furious."
Two rifles bought by a gun-smuggling ring that was being monitored through "Fast and Furious" were found at the scene. But authorities have declined to say whether the murder weapon was linked to a purchase from the operation.
Terry and other agents came under attack in a canyon north of the Arizona border city of Nogales by Osorio-Arellanes and four other men who had come to the U.S. to rob marijuana smugglers, investigators have said. Authorities have declined to say which of the five men fired the shot that killed Terry.
Osorio-Arellanes, of El Fuerte in the Mexican state of Sinaloa, was shot during the gunfight and has been in custody since the night of the shooting. Osorio-Arellanes told investigators he raised his weapon toward the agents during the shootout but didn't open fire, the FBI said.
As part of the plea, Osorio-Arellanes acknowledged sneaking into the United States from Mexico with others about a week before Terry's death. Group members retrieved guns and food supplies that they had hidden in the U.S. near the border for the robberies.
Osorio-Arellanes said in court papers that the group encountered Terry and three other Border Patrol agents on the night of the agent's death as the rip-off crew was searching for smugglers to rob.
Sentencing has been set for Jan. 11 by U.S. District Judge David Bury. Osorio-Arellanes' attorney, Clay Hernandez, declined through an assistant to comment on Tuesday on the plea.
"Today's plea is an important step in seeking justice on behalf of Agent Terry," Laura Duffy, the top federal prosecutor in San Diego whose office is prosecuting the case, said in a statement.
"Operation Fast and Furious" was launched in 2009 to catch trafficking kingpins, but federal agents lost track of about 1,400 of the more than 2,000 weapons - including AK-47s and other high-powered assault rifles.
Some of the guns purchased illegally with the government's knowledge were later found at crime scenes in Mexico and the U.S.
Critics have hammered federal authorities for allowing informants to walk away from Phoenix-area gun shops with weapons, rather than immediately arresting suspects and seizing firearms.
The two guns found at the scene of the Terry shooting were bought by a straw buyer for a smuggling ring suspected of purchasing guns for the brutal Sinaloa cartel, according to investigators.
Jaime Avila, 25, has admitted in court to buying the two guns and has pleaded guilty to gun charges in a smuggling case that's separate from the prosecution into Terry's death.
Avila, who isn't charged in Terry's death, faces up to 10 years in prison when he's sentenced on Dec. 12.
Of the four other men charged in Terry's death, one is in custody, while three others remain fugitives.
Authorities have offered a $1 million reward for information leading to their capture. FBI said it continues to aggressively pursue the three fugitives.
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