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Hours after a U.S. Border Patrol agent was shot and killed, and one other was shot and injured, James Turgal, FBI Special Agent in Charge Phoenix, arrives to speak at a news conference at the U.S. Customs and Border Protection Brian A. Terry Border Patrol Station, Tuesday, Oct. 2, 2012, in Bisbee, Ariz. (AP Photo/Ross D. Franklin)

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)