In this Monday, Dec. 24, 2012 file photo, Afghan police officers stand guard outside of Kabul police headquarters, where a an American contractor was killed, in Kabul, Afghanistan. On Tuesday, Dec. 25, 2012, the Interior Ministry said a policewoman, identified as Sgt. Nargas, who shot and killed 49-year-old Joseph Griffin in Kabul on Monday, was a native Iranian who came to Afghanistan and displayed "unstable behavior" but had no known links to militants. It was the first such shooting by a woman in the spate of insider attacks. On Wednesday, Dec. 26, 2012, a suicide bombing at the gate of a major U.S. military base in eastern Afghanistan killed the attacker and three Afghans, Afghan police said. The Taliban claimed responsibility for the attack. NATO forces and foreign civilians have also been increasingly attacked by rogue Afghan military and police, eroding trust between the allies. (AP Photo/Musadeq Sadeq)