(KCEN) -- Secretary of Homeland Security Janet Napolitano is visiting Arizona today to express her condolences to the family of a border agent killed this week.
On Tuesday, 30-year-old Nicholas Ivie was shot to death near Naco, Arizona, near the Mexico border.
The U.S. Customs and Border Protection Agency say Ivie and two other border patrol agents were responding to a motion sensor that was activated near the border.
Federal investigators say they cannot rule out the possibility of friendly fire.