Update: I’m adding CBS’s video report at the top of the post.

Original post follows …

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A lone shooter has shot several people at the Washington Navy Yard in DC, with local and military police responding to the gunfire.  There’s not a tremendous amount of information yet, but NBC and CBS have flash reports on the situation:

Police are searching for an active shooter on the grounds of the Washington Navy Yard after several people were shot Monday morning.

The U.S. Navy says three shots were fired at 8:20 a.m. at building #197 at the Naval Sea Systems Command headquarters. Several people have been shot, News4’s Jackie Benson reported. Benson says the suspect is inside a military building and is armed with a rifle.

Local CBS affiliate WUSA has more:

A police official says they received the report at 8:26 a.m.  Police are looking for a shooter in a military building near 8th and M Street SE.

The official says they do not know how many people may have been shot. According to the Associated Press, there is at least one victim.

DC Fire EMS units are on the scene. Fire officials say there are victims, but there is no confirmation of numbers yet. Officials say a medic unit, ambulance, and an engine company are responding as well as some EMS supervisors.

The Naval Yard houses the offices of the chief of Naval Operations, so this may or may not be a so-called local crime story.  I’ll update this post as more comes in.

Update: The comms director for Rep. Steven Horsford (D-NV) tweeted out this photo:

From one of our staffers sheltering in place in SE DC. #NavyYardShooting pic.twitter.com/UNcWqRLExY

— Tim Hogan (@timjhogan) September 16, 2013

Update (9:41 am ET): The Washington Post reports that the gunman has barricaded himself into a single room now:

A police spokesman confirmed at 9:20 a.m. that the officer was shot near the room where a lone gunman has barricaded himself after allegedly shooting at least three people on the Navy Yard grounds in Southeast Washington.

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.

That’s good news, if the police can contain him there.  Hopefully the injured will survive their wounds.

Update (9:47): Reagan National Airport has imposed a “ground stop” until the situation is secured:

RT @wtop: A ground stop is in effect at Reagan National Airport due to the incident at the Washington Navy Yard. http://t.co/Y9ea8XOXN6

— Julie Moos (@juliemmoos) September 16, 2013

And NBC reports seven wounded, including two police officers:

U.S. Navy Yard shooting latest: Seven people shot, including two police officers – @PeteWilliamsNBC

— NBC News (@NBCNews) September 16, 2013

Update (10:13): NBC reports four fatalities:

NBC reporting four dead, eight wounded in Navy Yard shooting.

— Sam Stein (@samstein) September 16, 2013

Update (10:17): More than one shooter? WaPo says three, according to police sources:

Developing: Police say 3 gunmen behind rampage at Washington Navy Yard: : http://t.co/xmc8OVPvTJ

— David Beard (@dabeard) September 16, 2013

But MSNBC retracted their own report on that point:

Update: MSNBC misspoke. Only one shooter known of. RT @BenHowe: @RachelleFriberg being told they said they misspoke.

— Rachelle (@Shelly__Marie) September 16, 2013

Everything in my timeline still suggests a lone gunman.

Update (10:21): WaPo sticking with three gunmen, according to police spokeswoman:

Police say three shooters, including at least one in fatigues, have shot at least 10 people at the Washington Navy Yard on Monday..

Police said at least one of the shooters is “down,” but it was unclear whether that means the suspect has been arrested or shot. Two remain 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.

I’m wondering if the police are getting confused on this point, so take this with a grain of salt for the moment.

Update (noon): I’ve waited a while to post another update, simply because media reports became too contradictory to determine what was accurate.  Most now are reporting a single gunman has been killed in the standoff:

At least one gunman opened fire inside a building at the Washington Navy Yard on Monday morning, and officials said several people were killed and as many as 10 were wounded, including a law enforcement officer.

A shooter had died, though it wasn’t immediately clear how, according to a Defense Department official and federal law enforcement official who spoke on condition of anonymity because they were not authorized to discuss the matter publicly. Two other officials have said police were looking into the possibility of a second shooter.

It appears that the shooter was a disgruntled worker:

More from @PeteWilliamsNBC based on info we have and are second sourcing, sounds more and more like a disgruntled worker behind shooting

— Chuck Todd (@chucktodd) September 16, 2013

Details on #NavyYard shooter: Source tells @PierreTABC shooter was a former Navy official in his 50's whose work status recently changed

— ABC News (@ABC) September 16, 2013

We’ll certainly find out more in the hours to come.