Update 1:25 pm:

NORFOLK, Va. — A civilian who boarded a guided-missile destroyer at the world's largest naval base disarmed a guard and killed a sailor, the Navy said Tuesday.

That man also was killed after he fatally shot the sailor who came to the aid of the petty officer on watch, the Navy said.

The incident occurred at about 11:20 p.m. ET Monday at Pier 1 aboard USS Mahan, base spokeswoman Terri Davis said. She didn't know whether the suspect had permission to be on board, but he was authorized to be on base.

The civilian suspect approached the destroyer's quarterdeck, and the ship's security personnel confronted him, Navy officials say. A struggle occurred, and the suspect was able to disarm the petty officer of the watch.

The suspect, who previously was unarmed, used the weapon to kill a sailor who came to the aid of the guard. He was killed; no other injuries were reported.

"I want to be clear: The suspect did not have his own weapon," said Capt. Robert Clark, Naval Station Norfolk's commanding officer.

The identities of the suspect and sailor will be released when their families are notified, Clark said. Counselors from Navy Fleet and Family Service Center are on hand to assist personnel.

"We'll find out what happened, and we'll prevent that from occurring again," Adm. Bill Gortney, commander of U.S. Fleet Forces Command based in Norfolk, said to a group of sailors gathered for a training session unrelated to the shooting.

The base was briefly put on lockdown for about 45 minutes as a precaution. With the exception of Pier 1, the first of 13 main piers, operations have returned to normal at Naval Station Norfolk, Davis said.

"The investigation has just begun, and right now there is a great deal of information we don't know just yet," Clark said.

The Mahan, commissioned in 1998, has a crew of nearly 300. In September, it returned to Norfolk after a deployment of more than eight months that included being positioned in the eastern Mediterranean for a potential strike against Syria.

To get on the Naval base, civilians must be escorted or have identification that allows them to be there. Authorized civilians can include Department of Defense employees, contractors and military family members.

"It's going to make us look at our procedures to make sure we're doing everything we need to do," Clark said. "I think we're making improvements every day to our security to make sure we stay safe."

The Norfolk base covers more than 6,000 acres and is the home port for 64 ships, according to information the Navy provided in February. About 46,000 military members and 21,000 civilian government employees and contractors are assigned to the base and its ships.

The base also is the home port for a Navy hospital ship, docked at Pier 1 with the Mahan.

Each base entrance is guarded, and motorists present IDs. Inspections are rare. All 13 piers have additional security forces. As part of ongoing security efforts, handheld ID scanners were put in place this year at Navy bases in the region, including the Norfolk station.

The shooting comes a week after the Navy began to study recommendations following September's mass killing at Washington Navy Yard, about 150 miles away, in which a contractor and former Navy reservist killed 12 civilian workers before being shot to death.

The shooting also comes about a month after the Navy had anti-terrorism and force protection exercises around the world, including an active-shooter drill at Naval Station Norfolk.

Contributing: The Associated Press

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NORFOLK, Va. (AP) — A base spokeswoman says two people were killed in a shooting at Naval Station Norfolk.

Terri Davis says the shooting happened around 11:20 p.m. Monday at Pier 1 on the base. Davis would not describe the circumstances of the shooting but said the scene is secure, no shooter was taken into custody and no one is being sought by authorities.

Davis says the two killed were a sailor and a civilian. No other injuries were reported.

The base was briefly put on lockdown after the shooting but that has since been lifted.

The shooting is under investigation.

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