This undated photo provided by U.S. Customs and Border Protection shows U.S. Border Patrol agent Brian A. Terry. / AP/U.S. Customs and Border Protection
A Mexican man has pleaded guilty to first-degree murder in the death of Border Patrol Agent Brian Terry, the first conviction in the federal agent's killing.
Prosecutors say Manuel Osorio-Arellanes was "part of an armed group of illegal aliens" that got into a firefight with Terry and his colleagues on Dec. 14, 2010.
Osorio admitted that his group crossed from Mexico into Arizona to rob drug traffickers who were also sneaking across the border.
Two rifles found at the scene after the suspects fled were part of the Bureau of Alcohol, Tobacco and Firearms gunwalking operation known as "Fast and Furious."
In that case, ATF allowed thousands of weapons to "walk" into the hands of Mexican drug cartels, instead of interdicting the weapons and arresting the suspects as soon as a case could be made.
Supporters of the controversial tactic say the idea was to see where the guns ended up, and try to make a big case against a Mexican drug cartel kingpin.
After Terry's murder, ATF agents who disagreed with the gunwalking strategy because they said the guns that ATF "let go" could be used to kill innocent people, stepped forward and blew the whistle. That includes ATF Special Agent John Dodson who spoke first to CBS News.
Ultimately, a lengthy inspector general investigation faulted officials in the Department of Justice, ATF and the Arizona U.S. Attorney's Office for management failures in the gunwalking case.
The FBI is still looking for three fugitives in Terry's murder, all Mexican citizens: Jesus Rosario Favela-Astorga, Ivan Soto-Barraza, and Heraclio Osorio-Arellanes. Another defendant, Lionel Portillo-Meza was captured in Mexico in September and is still awaiting extradition to the US.
Osorio will be sentenced on Jan. 11, 2013. He faces up to life in prison. Under a plea agreement, the US Attorney's office agreed not to seek the death penalty.