An update to this story, originally published at 12:12 p.m. ET, March 24, can be found here.
A Naval hospital in San Diego is on lockdown after an anonymous caller reported an active shooter inside a building with other gunmen possibly on the way, according to a Defense official.
The call matched another report of a patient seen with a weapon, according to the official who was not authorized to speak publicly. All personnel were ordered to shelter in place and police were responding to the scene.
A similar report that turned out to be false came at the same naval hospital in January.
Officials scoured buildings and grounds with dogs in January but found no evidence of a gunman or shots having been fired.
The medical center is also called the Bob Wilson Naval Hospital. It is located on the grounds of Balboa Park in San Diego and provides advanced treatment facility as well as serving as a major teaching and research center. About 500 people work there.
On Thursday, security personnel found and a bullet on the floor in one of the buildings, the official said. A caller reported a patient with a gun and then hung up.
Police with dog teams are at the hospital investigating, the official said.
