Shots Fired at the Naval Sea Systems Command Headquarters Building in DC … 5 People Shot … Active Search for Gunman (Update: 10 People Wounded) (Update: 2 Shooters, 4 Dead, 8 Wounded) (Update: 12 Killed)

At 8:20 am at the US Naval Sea Systems Command HQ in Washington, DC, shot were fired. As reported at Navy.mil, Several people were injured in a shooting at the Washington Navy Yard, including a police officer.

From CBS DC: Authorities have reportedly described the suspect as a bald black male dressed in all black, possibly carrying an assault rifle and a double-barreled shotgun. Law enforcement officials believe the suspect is still in the building.

VIDEO – CNN

The U.S. Navy said that three shots were fired around 8:20 a.m. at the Naval Sea Systems Command Headquarters building, where about 3,000 people work.

Police said that at least three, possibly four, people were shot. All are in critical condition, authorities said.

A “shelter in place” order has been issued for Navy Yard personnel, authorities said.

Police closed the 11th St Bridge as well as M St SE between 2nd and 4th streets SE due to the shooting. Entrances to the Navy Yard Metro station remain open.

UPDATE I: At least five people have been shot at the Washington Navy Yard and an active shooter is still on the base grounds in Southeast D.C.

The U.S. Navy says shots were fired at 8:20 a.m. Monday at the Naval Sea Systems Command Headquarters building. D.C. police confirm that at least five people, including one D.C. police officer and one base officer, have been shot.

The Navy Yard is on lockdown and a “shelter in place” order has been issued, the Navy says. About 3,000 people work in the building, the Navy says.

The 11th Street Bridge is closed in both directions. M Street is closed near New Jersey Avenue near 11th Street.

Ronald Reagan Washington National Airport has a ground stop due to “security,” according to the Federal Aviation Administration website. The FAA says all departures have been grounded until at least 10:30 a.m.

UPDATE II: Pics and Tweets from Mediaite.com.

UPDATE III: From the WAPO … Police believe they have pinned down a shooter who has been firing at people in the Washington Navy Yard wounding at least 10 people.

Police said that they believe the shooter is somewhere between the third and fourth floors of one of the buildings on the installation in Southeast Washington, but they declined to identify it further.

Police on the scene said eight civilians were shot, along with the two police officers. One is a D.C. Metro Police officer who was shot two times in the leg, police said. The other officer worked at the base.

UPDATE IV: Police say 2 shooters have killed 4, injured 8 on grounds of Washington Navy Yard.

Police now believe two shooters, including one in fatigues, have killed four people and wounded eight others at the Washington Navy Yard on Monday, throwing the region into fear and chaos during the morning commute.

At least one of the shooters is “down,” police said mid-morning, but it was unclear whether that means the suspect has been arrested or shot. They said the other suspect remains at large, and police believe they have pinned down one between the third and fourth floors of one of the buildings on the installation in Southeast Washington.

Visit NBCNews.com for breaking news, world news, and news about the economy

UPDATE V: Gunman kills at least 12 at Washington Navy Yard, gathering weapons along the way.

A former petty officer who apparently had a grudge against the Navy sprayed an office building with bullets at the Washington Navy Yard on Monday, killing 12 people in a rampage that paralyzed part of the nation’s capital, authorities said.

Authorities said the gunman, a civilian contractor and former Navy reservist they identified as Aaron Alexis, 34, was killed after exchanging fire with officers who stormed the headquarters of the Naval Sea Systems Command in a massive law enforcement response.