Police say a gunman opened fire at the Washington Navy Yard Monday morning, killing 12 people and triggering an hours-long manhunt and lockdown blocks away from the U.S. Capitol building.

Officials confirmed the shooter, Aaron Alexis, was killed in a confrontation with law enforcement, bringing the total dead to 13. A search was continuing for a black male in his 40s or 50s described as wearing green military-style clothing. The D.C. police department said in a tweet that a white male initially being sought was not a suspect or a person of interest.

As It Happened: Mass Shooting at Washington Navy Yard

Emergency vehicles and law enforcement personnel respond to a reported shooting at the Washington Navy Yard, Sept. 16, 2013 in Washington, D.C. (Getty Images)

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6:20 p.m. An FBI official tells TheBlaze that the second person being sought is more than likely “going to be cleared.”

The Joint Terrorism Task Force is involved in the investigation, however “the motive has not yet been determined,” the FBI official said. “We are attempting to trace (Alexis’) steps, where he’s been, who he’s been talking too and who he’s been staying with prior to the shooting.”

6:16 p.m. D.C. police chief Cathy Lanier tells reporters the D.C. police officer shot is now stable, out of surgery and will be OK.

5:51 p.m. The Seattle Police Department says Alexis was arrested in 2004 for shooting out the tires of another man’s car, which Alexis described to detectives as an anger-fueled “blackout.”

5:30 p.m. The FBI is asking the public for any information about Aaron Alexis.

5:15 p.m. From Dallas Fox affiliate KDFW-TV:

Alexis’ roommate until about four months ago was Fort Worth man Nutpisit Suthamtewakul. Suthamtewakul told FOX4 on Monday he lived with Alexis for three years.

He described Alexis as a great guy and was stunned to find out about the shootings in Washington DC and Alexis’ link to them.

Suthamtewakul said Alexis had a concealed handgun license and worked as a computer tech and spoke Thai. In his free time, Alexis spent time at a local Buddhist temple.

Suthamtewakul said when Alexis was without a job, he let him work at a Thai food restaurant he owned, called Happy Bowl Thai.

4:55 p.m. Here’s everything we know so far about Aaron Alexis: September 2010 arrest for accidental discharge of a firearm, and a former avionics electrician for the Navy.

As It Happened: Mass Shooting at Washington Navy Yard

In this handout photo provided by the FBI, Aaron Alexis is shown in a photo prior to the mass shooting at the Washington Navy Yard on Sept. 16, 2013 in Washington, D.C. Authorities believe Alexis was a gunman involved in the shootings at the Navy Yard, where at least 12 people were shot and killed. (Getty Images)

4:24 p.m. Valerie Parlave, assistant director in charge of the FBI’s Washington field office, confirmed the deceased shooter is  34-year-old Aaron Alexis of Fort Worth, Texas.

4:20 p.m. D.C. Mayor Vincent Gray confirms an updated death toll of 13, including the shooter. One more person died either at or en route to the hospital.

The mayor said there is still another person being sought who was identified in video.

“We don’t have any reason at this stage to suspect terrorism but it has certainly not been ruled out,” Gray said.

4:20 p.m. Statement from House Armed Services Committee Chairman Buck McKeon (R-Calif.) and ranking member Adam Smith (D-Wash.):

“We’re saddened by today’s heartbreaking attack at the Washington Navy Yard. Unfortunately, this is not the first time we’ve seen such a tragedy befall the patriotic personnel working at a U.S. Military installation. There is nothing more cowardly than targeting innocents, and we have full faith in military and law enforcement officials to bring the perpetrators to justice.  We send our thoughts and prayers out to the victims and their families.”

4:17 p.m. Senior FBI source to TheBlaze: “We have not ruled out the possibility of other shooters present, but right now all we know of is one.”

4:15 p.m. Via NBC Dallas Fort Worth, Aaron Alexis’ 2010 arrest report.

4:05 p.m. Dr. Janis Orlowski, chief operating officer at Washington Hospital Center, told reporters three shooting victims are all in stable condition. One, a D.C. police officer, was shot in the legs and was still in surgery. A woman was in surgery for a shoulder injury, and another woman injured in the hand and in the head but without the bullet penetrating her skull would not need surgery, Orlowski said. The two women were civilians, Orlowski said.

3:45 p.m. The Associated Press and Washington Post have both confirmed the identity of the deceased shooter as Aaron Alexis.

As It Happened: Mass Shooting at Washington Navy Yard

The dead gunman has been identified by NBC News, the Associated Press and The Washington Post as Aaron Alexis, 34, from Texas. (Image source: NBC Washington WRC-TV video still)

3:29 p.m. Fox News reports it has also confirmed the name of the deceased shooter as Aaron Alexis.

3:23 p.m. The U.S. Senate complex has been placed on lockdown in light of the shooting.

3:15 p.m. According to NBC Washington, video footage shows one gunman entering the building with a shotgun. He reportedly shot a security guard and then proceeded on through the building, possibly with the security guard’s pistol. He may have hidden in wait for responding police officers, then opened fire, shooting one D.C. officer in the leg and then may have retrieved that officer’s AR-15 rifle.

The white male in the tan outfit has been identified and is not a suspect or person of interest.
As It Happened: Mass Shooting at Washington Navy Yard
@DCPoliceDept
DC Police Department

2:29 p.m. NBC Washington is reporting the deceased shooter is a 34-year-old Texas man who was using a former employee’s identification. NBC News reported the shooter’s name is Aaron Alexis and he had been working as a civilian contractor himself.

2:15 p.m. D.C. police chief Cathy Lanier says they are still searching for a white male, 40 to 50 years of age, wearing a tan military-style uniform, and a black male, 40 to 50 years of age, wearing a green military-style uniform, described as having a medium complexion and gray side burns.

“Multiple piece of information that would suggest there are at least two other individuals that were seen with firearms,” Lanier said. “These are people that we believe are involved in some way.”

Police are still conducting an “extensive” search, she said. “This is a large base.”

2:08 p.m. D.C. police chief Cathy Lanier confirms one officer was injured by gunfire. She says the FBI will now take the lead on the investigation.

2:07 p.m. Washinton, D.C. Mayor Vincent Gray told reporters it appears there are “at least 12″ fatalities. No known motive at this stage.

2:03 p.m. The Washington Post reports the death toll has risen to nine, including the gunman.

2:00 p.m. Fox News reported on the air that a Navy spokesman sent one line: “This is not over.”

1:33 p.m. Here’s a map showing the layout of the Washington Navy Yard.

1:25 p.m. Air Force Sgt. David Reyes told TheBlaze his wife works in human resources in the building next to where the shooting took place. She is still on lockdown, and texted him that everyone inside is very worried and hungry.

1:16 p.m. An FBI official confirms to TheBlaze that a name widely reported to be that of the shooter is inaccurate.

12:57 p.m.

As It Happened: Mass Shooting at Washington Navy Yard

A military guard outside a parking garage near the Washington Navy Yard. (Photo credit: TheBlaze/Eddie Scarry)

12:43 p.m. CBS News reports the shooter has been identified as Chief Navy Petty Officer Rollie Chance. UPDATE: CBS says its report identifying Rollie Chance is wrong.

12:34 p.m. President Barack Obama addressed the shooting during a previously scheduled event.

“I’ve been briefed by my team on the situation. We still don’t know all the facts but we do know that some people have been shot and some have been killed. We are confronting yet another mass shooting and today it happened on a military installation that targeted military and civilian personnel,” Obama said.

Obama called those targeted “patriots” who “know the dangers of serving abroad, but today they faced the unimaginable violence that they wouldn’t have expected here at home.”

“We will do everything in power to mark sure whoever carried out this cowardly act is held responsible,” Obama said.

12:16 p.m. D.C. police chief Cathy Lanier has confirmed that one shooter is deceased, but police are searching for two other potential gunmen.

“We potentially have two other shooters that we have not located at this point,” Lanier said. They include: a white male who was last seen around 8:35 a.m. with a handgun; and a black male, approximately 50 years of age, who may have been carrying a long gun. Both were wearing military-style uniforms but there is no information that they are military personnel, Lanier said.

11:43 a.m. CNN is reporting a Navy spokesman says there are “multiple deaths” and two shooters are “down.”

11:42 a.m. The Associated Press is reporting the shooter has died

11:35 a.m. Patricia Ward said she was in the cafeteria when she heard gunfire.

“I heard the first three shots, pop pop pop. And we all knew I know what a gun sounds like,” Ward said.

11:32 a.m. NBC Washington is reporting four police officers are down, including D.C. metro and military officers.

11:31 a.m. “All I hear is screaming”: Tweets from woman who says she was at scene of the shooting

11:29 a.m. Eyewitness says “people were shoving” and climbing the walls trying to get away

11:28 a.m. NBC Washington is reporting one shooter is dead, citing two law enforcement sources.

11:23 a.m. USA Today: Two shooters “down.”

11:25 a.m.

As It Happened: Mass Shooting at Washington Navy Yard

A Twitter user tweeted a photo apparently showing an injured person in the area of the Washington Navy Yard. (Image source: Tim Hogan/@timjhogan)

11:14 a.m. NBC News is reporting police have entered a second building; one suspect is reported to have been captured.

10:53 a.m. The Washington Post reports: “Police now believe two shooters, including one in fatigues, have killed four people and wounded eight others.”

10:48 a.m. U.S. Navy Band MU1 Joe Friedman told TheBlaze he was walking to work when word of the shooting spread. He said he was in shock.

“I have no idea how someone could accomplish that,” Friedman said.

As It Happened: Mass Shooting at Washington Navy Yard

A helicopter lifts a person off the roof as police respond to a report of a shooting at the Navy Yard in Washington, D.C. on Sept. 16, 2013. (AP)

10:35 a.m. Naval spokesman confirms reports of at least two shooters.

10:30 a.m. A U.S. Navy official told TheBlaze they cannot confirm the shooting is limited to one suspect.

10:26 a.m. NBC Washington is reporting there were at least 12 victims.

As It Happened: Mass Shooting at Washington Navy Yard

Heavy police presence at the Washington Navy Yard two hours after the shooting was first reported. (Photo credit: TheBlaze/Eddie Scarry)

10:16 a.m. “Happy Days” actor Henry Winkler reacts with tweet about gun control.

10:15 a.m. Associated Press: Defense official says several people killed, up to 10 wounded.

As It Happened: Mass Shooting at Washington Navy Yard

A group of people, mostly workers in the surrounding area, wait outside a Starbucks three blocks from the shooting location. (Photo credit: TheBlaze/Eddie Scarry)

10:06 a.m. The shooter may have been armed with an AR-15, NBC Washington reports.

10:04 a.m. Statement from a White House official:

“The President has been briefed several times about the unfolding situation at the Washington Navy Yard by Assistant to the President for Homeland Security and Counterterrorism Lisa Monaco and Deputy Chief of Staff Alyssa Mastromonaco. The President directed his team to stay in touch with our federal partners, including the Navy and FBI, as well as the local officials.  We urge citizens to listen to the authorities and follow directions from the first responders on site.”

#BREAKING: #USNavy confirms several injuries with reports of fatalities at #NavyYardShooting. More to follow.
As It Happened: Mass Shooting at Washington Navy Yard
@USNavy
U.S. Navy

9:58 a.m. NBC Washington reports at least 10 people have been shot.

As It Happened: Mass Shooting at Washington Navy Yard

Two police officers put their gear on as they respond to a report of a shooting at the Washington Navy Yard, Sept. 16, 2013 in Washington, D.C. (Getty Images)

9:54 a.m. Flights at Reagan National Airport have been halted.

9:47 a.m. Local news is showing a helicopter lowering a basket down, possibly to rescue a stranded victim.

9:46 a.m. NBC News is reporting seven people have been shot, including two police officers.

9:43 a.m. The suspect has been described as a black male approximately 6 feet tall, according to local ABC affiliate WJLA-TV. It is unclear whether he is military or a civilian.

9:33 a.m. The Washington Post reported a D.C. police officer is among those shot out of at least three, possibly four victims.

9:24 a.m. NBC Washington is reporting the search for the shooter is still active. The station reports two people were shot inside the building at the Naval Sea Systems Command, and one person possibly shot on the roof. There are also reports of at least one police officer shot.

Original post below:

#BREAKING: #USNavy confirms active shooter at Washington Navy Yard. More to follow.
As It Happened: Mass Shooting at Washington Navy Yard
@USNavy
U.S. Navy
Confirmed active shooter on the grounds of the Navy Yard with multiple victims
As It Happened: Mass Shooting at Washington Navy Yard
@IAFF36
DC Fire Fighters L36

Navy officials say a lone gunman opened fire and wounded “several victims,” NBC News is reporting.

NBC Washington affiliate WRC-TV reported a woman was shot and there was still an active search for the gunman as of 9:10 a.m. ET.

According to WRC, the Navy said three shots were fired at 8:20 a.m. inside a building that houses the Naval Sea Systems Command.

This is a breaking news story. Updates will be added.

TheBlaze’s Sara Carter and Eddie Scarry contributed reporting.