A US sailor allegedly killed two female sailors in their barracks in the Gulf state of Bahrain.
The alleged shooter, a male, was critically wounded in the incident in the barracks on the US Naval Support Activity Bahrain base.
An official did not say if the alleged killer had shot himself or if anyone else was involved in the incident, which was under investigation.
But the navy said the incident was not terror-related and only involved US military personnel.
The US navy's Fifth Fleet is based on the island state of Bahrain, which is a staunch ally of Washington.
The two victims died at the scene and the third was taken to hospital for emergency treatment.
An investigation has been launched and the base was temporarily closed as the barracks were combed for evidence.
The two women were pronounced dead at the scene, and the man was taken to a local hospital in critical condition, the navy official said.
The shootings came after Bahrain charged four nationals earlier this month with belonging to al-Qaida amid reports a cell was plotting attacks against US targets.
The Bahraini government has introduced tough new anti-terror laws despite strong opposition from local civil rights groups.