WASHINGTON : A sailor and a civilian died in a shooting incident aboard a destroyer at a US navy base in Virginia, the base commander said Tuesday.

The civilian was armed and apparently had authorization to be on the base, called Naval Station Norfolk, homeport to the US Atlantic Fleet, Captain Robert Clark told a news conference.

Clark gave few details, saying the case was under investigation, but suggested the civilian opened fire first on board the USS Mahan and was then shot by naval security forces. Clark would not say how the civilian obtained the weapon. Both fatalities were male, Clark said. He said the shooting around 11:20 pm Monday (0320 GMT) and would not speculate on what had caused it. The base was placed on lockdown for about 45 minutes but operations are back to normal except at Pier 1 where the shooting happened, Clark said.

Naval Station Norfolk is a sprawling complex that is the world’s largest naval facility, according to its web site.