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This undated photo provided by U.S. Customs and Border Protection shows Border Patrol agent Nicolas Ivie. Ivie was shot to death Tuesday, Oct. 2, 2012 in Arizona near the U.S.-Mexico line, the first fatal shooting of an agent since a deadly 2010 firefight with Mexican bandits that spawned congressional probes of a botched government gun-smuggling investigation. (AP Photo/U.S. Customs and Border Protection)

Border Patrol agent killing

The head of the U.S. Border Patrol agents'

union says the agent killed last week in a shooting in southern Arizona

apparently opened fire on two colleagues thinking they were armed

smugglers and was killed when they returned fire. (Oct. 8)