Afghan police officials are confirming that three civilian police training advisers killed Sunday, July 22 in western Afghanistan were American, AP reported.

German Brig. Gen. Gunter Katz, a spokesman for the U.S.-led coalition, says that a gunman wearing an Afghan police uniform shot the civilians in Herat.

NATO has not disclosed their nationalities, but two Afghan police officials in Herat said Monday they were all Americans.

The officials spoke anonymously because the incident is under investigation. They said the gunman, who was killed after he opened fire, had been in the police force for 1 1/2 years.

The officials say another adviser and an Afghan translator were wounded in the incident, which occurred inside a hall at an Afghan police training center south of Herat.

The fourth adviser's nationality is not known.