A U.S. Navy sailor shot and killed two civilian employees of the Defense Department and wounded a third, before killing himself at Hawaii's Pearl Harbor military installation.

Rear Adm. Robb Chadwick, commander of Navy Region Hawaii, said the shooting occurred near dry dock 2 in the Naval shipyard at Joint Base Pearl Harbor-Hickam.

Chadwick said the male shooter "has tentatively been identified as an active-duty sailor assigned to USS Columbia," a nuclear-powered Los Angeles-class fast attack submarine.

Chadwick said the names of the shooter and his victims would not be released until next-of-kin had been notified. He said the wounded civilian is in stable condition at a local hospital.

A motive for the shootings has not been identified and it is not known whether the victims were random or known to the shooter.

Joint Base Pearl Harbor-Hickam is home to nine Arleigh Burke-class destroyers, a guided missile cruiser and 15 attack submarines, plus the U.S. Air Force Pacific Command.