This story was updated at 5:22 p.m. to reflect new information:
D.C. Mayor Vincent Gray said during a 4 p.m. news briefing at least 13 people are dead - including one alleged shooter - in the wake of a shooting spree Monday morning at the Washington Naval Yard in the southeast corner of the city. He also said one of two potential additional suspects had been cleared from the case.
"Earlier today we talked about the possibility of there being two other suspects, one of those has been ruled out; that gentleman has been identified and is no longer a suspect," Gray said. "He's been talked to by law enforcement officials and there's no reason to continue any views that he may have been involved in this."
But law enforcement officials are still looking for another man, identified as wearing a drab olive uniform, around 50 years of age, approximately 5'10" and African-American.
"We don't know what the motive is at this stage¬but we don't have any reason at this stage to suspect terrorism," Gray said.
Valerie Parlave, assistant director in charge of the Washington field office of the FBI, also confirmed the identity of the deceased alleged shooter.
"We can confirm that the deceased shooter from this morning has been identified at 34-year-old Aaron Alexis of Fort Worth, Texas," she said. News reports have described him as a defense contractor who may have entered the secure building with someone else's identification card.
This story update was posted at 4:04 p.m.:
The dead suspected Washington Navy Yard shooter has been identified as Aaron Alexis, a 34-year-old from Texas by federal law enforcement officials, according to The Associated Press.
One of the anonymous tipsters told the AP Alexis likely used someone else's identification card to enter the secure facility.
Police continue to be on the lookout for at least one other potential suspect and are scheduled to hold a news update at 4 p.m.
This story update was posted at 3:02 p.m.:
At least 12 people are dead and eight people are injured as a result of the D.C. Navy Yard shooting spree Monday, according to local authorities.
D.C. Mayor Vincent Gray also confirmed during an afternoon news briefing that law enforcement is still investigating whether or not there was more than one shooter.
"Right now we are confirming at least 12 fatalities, we had a few additional folks who were injured, they were not fatally injured," said D.C. Police Chief Cathy Lanier, adding that several law enforcement officials are among the injured.
"A large part of the area is still on lockdown, we are asking the residents to stay out of the area and remain in your home," Lanier said. "We do feel like the area is safe, but we do still have an active search for potentially additional suspects."
The investigation has been handed over to the FBI and teams of investigators from multiple agencies are continuing to search the Navy Yard complex, a process that could take a couple more hours to complete, Lanier said.
"We have no indication of any motive at this time," she said. "At this point I think the actions of the police officers without question helped to reduce the number of lives lost."
Police continue to be on the lookout for two potential suspects.
"The first is for a white male between 40 and 50 years of age, wearing a tan, what appears to be military uniform consistent with a naval uniform and a beret-style hat," Lanier said. "We also have a lookout for a black male, between the ages of 40 and 50 and an olive, military-style uniform. He is approximately 5'10" and 180 pounds or medium complexion and graying sideburns."
Gray said the next briefing is scheduled for 4 p.m.
This story was originally posted at 12:51 p.m.:
At least six people have been killed and eight more injured in a shooting rampage at the Washington Navy Yard in the southeast corner of Washington, D.C., according to law enforcement officials.
One of the alleged shooters is now dead, according to The Associated Press, but law enforcement officials say they are on the lookout for up to two additional shooters who remain at-large.
"This is not confirmed, but we potentially have two additional shooters out there," said D.C. Police Chief Cathy Lanier, in a news briefing from the scene. "We have no reason to believe either of those folks are military personnel, but we do have information that those individuals are wearing military-style uniforms."
Lanier said one suspect was a white male who was last seen around 8:35 a.m. in a khaki military uniform, short-sleeved with a beret hat, and armed with a handgun and the other suspect was a black male approximately 50 years of age, may have been in possession of a long gun, and dressed in an olive-drab colored uniform.
Officials said following the 8:20 a.m. initial shooting, the suspect was contained at the Naval Sea Systems Command headquarters where the shooting took place.
"A shooter entered the building … and began shooting," said D.C. Mayor Vincent Gray, in a news briefing. "We're still trying to confirm the number of fatalities involved. As far as we know this is an isolated incident. We would ask all the residents of this area to stay out of this area."
One metropolitan police officer is currently undergoing surgery at MedStar Washington Hospital Center and two other victims are being prepped for surgery, according to a hospital spokeswoman.
"We have been in discussions with individuals who are at the scene and we understand there are still more victims and we are not sure as yet how many individuals are coming to our hospital," said Jans Orlowski, chief medical officer for MedStar Washington Hospital Center.
Orlowski said all three victims at the hospital suffered critical injuries but their chances for survival are high.
The police officer suffered multiple gunshot wounds to his legs; one female victim was shot in the shoulder and another female suffered a gunshot wound to her head and her hand, according to Orlowski.
"Reports from victims mean it must have been a semi-automatic weapon," she added. "They have not been able to give us any information about what happened to them; they are obviously in pain and in distress from what they suffered this morning."
Police, fire and rescue forces swarmed the scene soon after the initial reports of the shooting. About 3,000 people – civilian and military – work at the Naval Sea Systems command headquarters where the shooting allegedly took place and have been asked to "shelter in place" following the initial reports of the incident.
As a result of the law enforcement and medical helicopter presence, air traffic at Ronald Reagan National Airport had been restricted, but that ban has now been removed, according to reports.President Barack Obama, who has been briefed several times on the incident, according to the White House, is also expected to comment on the shooting during a previously scheduled news conference on economic issues.
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Updated 9/16/13: This story was last updated at 5:22 p.m. to reflect new information.