49-year-old Joseph Griffin, from Mansfield, Georgia, was shot and killed in Kabul on 24th December 2012.
His killer was a policewoman identified only as Sergeant Nargas, an Iranian who went to Afghanistan 10 years ago with her husband and obtained a fake ID through him, according to a report in The Guardian.
Mr Griffin was employed by US-based DynCorp International and was in the country supporting the Afghan Ministry of Interior and Afghan National Police Development Program (AMDP).
Nargas walked into a heavily-guarded compound in the heart of Kabul, confronted Griffin and shot him with a pistol. Investigators are still unclear on a motive for the attack.
Afghan government spokesman, Sediq Sediqi, told a news conference that Nargas, in her early 30s and a mother of four, was born in Tehran and moved to Afghanistan 10 years ago after marrying an Afghan national. She joined the Afghan police five years ago and had a clean record within the force.
He went on to say that "her mental condition is not good," and described her as "unstable." He also told press that she had recently attended a training course in Egypt and had been assessed as "not being normal," in a reference to her mental state.
A statement on the DynCorp International website stated that Mr Griffin had worked in support of several of the company's global training and mentoring programs since November 2000 and that he deployed to Afghanistan in July 2011. The statement also says about Mr Griffin that he was "A veteran of the U.S. military who served in various U.S.-based law enforcement positions over the years, Mr. Griffin was an experienced professional who will be missed by his colleagues.