- Two American civilians also were wounded in the attack, Defense Department says
- The attack happened near base outside Kabul, the department says
Two US civilians were wounded and are in stable condition, the department said in a statement.
A US official said the attack occurred at an Afghan military ammunition supply point near Camp Morehead outside Kabul.
The attacker opened fire at the entry control point and was later killed, the US official said.
The Americans were performing duties as part of the larger NATO mission to train and assist Afghan security services, the Defense Department said.
The casualties are not being identified until next of kin are notified.
"Anytime we lose a member of our team, it is deeply painful," said Gen. John W. Nicholson, commander of US Forces-Afghanistan and Resolute Support. "Our sympathies go out to the families, loved ones and the units of those involved in this incident."