Four people were killed and eight more were wounded Monday at the Washington Navy Yard when gunmen armed with assault rifles barged inside and opened fire, officials said.
Police shot one of the intruders, who later died of his wounds, the Associated Press reported.
The other was believed to be pinned down in the Naval Sea Systems Command Headquarters building, besieged by police, according to local media.
Two police officers were reportedly among the wounded, including a Washington D.C. cop who was hit twice in the legs and was evacuated by helicopter.
The other victims were all said to be civilians who work at the base in southeast Washington, local media reported.
It was not immediately clear who the gunmen were, but everybody from SWAT teams to the Marines were on the scene and overhead a half-dozen military choppers were circling the base.
Navy yard workers interviewed by CNN said they were fired on in a hallway by a rifle-toting gunman who opened fire without any warning.
“He was tall,” Terry Durham said. “He appeared to be dark-skinned.”
“He was a tall black guy,” said her co-worker, Todd Brundage, who is also black. “He didn’t say a word.”