A sailor was fatally shot and killed at Naval Station Norfolk in Virginia and security forces have killed the male civilian suspect, a base spokeswoman said.
The shooting happened around 11:20pm on Monday aboard the USS Mahan, a Navy destroyer, spokeswoman Terri Davis said.
Davis would not describe the circumstances of the shooting but said the scene was secure.
Davis said the two killed were both males but she did not have any other information on them. She could not say if the civilian had permission to be aboard the ship.
No other injuries were reported, according to the Associated Press.
The base, the largest naval installation in the world, was briefly put on lockdown after the shooting as a precaution, but the lockdown was later lifted.
Operations have returned to normal at the base, with counsellors available, the Navy said in a news release, but enlisted sailors on the Mahan were not to report to duty Tuesday.
"We were able to secure the installation for that brief period till we determined that the suspect was taken care of and then therefore we were able to open up the installation because we didn't have any other threats so we're back at normal operations at Naval Station," said Naval Station Norfolk Commander Captain Robert Clark Jr.
To get on the base, civilians must be escorted or have a pass. The shooting was under investigation.
In September, a gunman killed 12 civilian workers before being shot to death at the Washington Navy Yard.