An Afghan soldier opened fire on Tuesday at a training base in northern Afghanistan, killing two US civilian trainers and another Afghan soldier.
NATO says the shooter was also killed in the incident at Camp Shaheen, outside Mazar-e-Sharif.
One NATO soldier and an Afghan soldier were wounded.
A renegade soldier last week killed three members of a British Gurkha regiment, before escaping, in Helmand province.
About 150,000 US and NATO troops are in Afghanistan fighting the Taliban.