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    Christy Ivie, center, wife of Nicolas Ivie, holds back tears as she is surrounded by her family, her father Tracy and mother DeAnn Morris, left, and her sister, Jan Cloward, right front, and brother, Travis Morris, right back, during news conference about slain U.S. Customs and Border Protection agent Nicolas Ivie, on Thursday, Oct. 4 , 2012, at the Cochise College in Sierra Vista, Ariz. Ivie was gunned down Tuesday, Oct 2, as he responded to a tripped sensor on the USA side of the border fence, near the small border town of Naco, Ariz. Ivie's partner was also hit in gunfire during the exchange, but was released from a Tucson hospital on Wednesday. (AP Photo/Gary M. Williams)

    Christy Ivie, center, wife of Nicolas Ivie, holds back tears as she is surrounded by her family, her father Tracy and mother DeAnn Morris, left, and her sister, Jan Cloward, right front, and brother, Travis Morris, right back, during news conference about slain U.S. Customs and Border Protection agent Nicolas Ivie, on Thursday, Oct. 4 , 2012, at the Cochise College in Sierra Vista, Ariz. Ivie was gunned down Tuesday, Oct 2, as he responded to a tripped sensor on the USA side of the border fence, near the small border town of Naco, Ariz. Ivie's partner was also hit in gunfire during the exchange, but was released from a Tucson hospital on Wednesday. (AP Photo/Gary M. Williams)

    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)