The incident took place late Wednesday when the person "turned his weapon against coalition service members," the U.S. military said. The person who opened fire was killed by coalition forces who returned fire, the military said.
A U.S. Defense official said the incident occurred near Kandahar. He didn't know the service member's branch of service or if anybody was wounded from the gunfire.
The Afghan and U.S. military are investigating.
It is unclear whether the shooter was an Afghan soldier or an infiltrator wearing the uniform.