By Daily Mail Reporter PUBLISHED: 07:49 EST, 31 October 2012 | UPDATED: 09:07 EST, 31 October 2012 A Mexican robber has admitted murdering a U.S. Border patrol agent whose death revealed a failed federal gun smuggling operation. Manuel Osorio-Arellanes pleaded guilty to killing agent Brian Terry in 2010 - the highest profiel conviction in the case which has embarrassed the federal government and prompted a series of congressional investigations. The killer also confessed to being part of a criminal gang who crossed into the country a week earlier to rob marijuana smugglers, stashing guns and food supplies. Manuel Osorio-Arellanes, pictured, has pleaded guilty to murdering U.S border agent Brian Terry and admitted being part of a robbery gang
@highlight
Brian Terry was shot dead in 2010 near the U.S/Mexican border of city of Nogales, in Arizona
@highlight
Manuel Osorio-Arellanes, one of five suspected of the shooting, has pleaded guilty to murder
@highlight
Mr Terry's death exposed a failed government gun-smuggling operation which saw officers lose track of more than 1,000 guns
Terry and three other agents came under attack in a canyon north of the Arizona border city of Nogales by @placeholder and his four other gang members, investigators said.