NORFOLK, Va. (AP) — -

A military official familiar with the investigation says the civilian who fatally shot a sailor aboard a Navy destroyer came onto the installation in a tractor-trailer and was killed by a sailor assigned to the ship.

The Navy has said the civilian carried a transportation worker's credential that authorized him to be on Naval Station Norfolk.

The Navy has said the civilian came onto the base unarmed and took a gun from a sailor standing watch on the USS Mahan, then used that weapon to shoot a responding sailor.

The official says the victim was the chief of the guard, a security role. His father has identified him as Mark Mayo from Maryland.

The official spoke on condition of anonymity because the person was not authorized to publicly release the information about the civilian or the victim.