Naval Medical Center Portsmouth was briefly under a "Code White," on Tuesday morning, which refers to an active shooter in the building.
Navy emergency personnel responded to a report of gunshots fired on the grounds, which prompted the lock down around 9:30 a.m.
According to Navy officials, the incident did not occur in the hospital's buildings, but in the barracks located on the grounds.
They say a sailor was found dead in his barracks room while security was looking for the source of the gunfire.
The hospital was given the "all-clear" about 15 minutes later and has since been reopened for normal operations.
Naval Criminal Investigative Service is investigating to determine the cause of death.
The Navy does note that the "Code White" was sent out as a precaution and that an "active shooter" was not spotted.
Updates will be posted here as they become available.