WASHINGTON, Sept. 16 (Xinhua) -- At least 12 people were confirmed dead in the Washington Navy Yard shooting on Monday morning, and the police were searching for other potential suspects, police officials said.
One suspected shooter was killed on site, said Cathy Lanier, chief of Washington Metropolitan Police Department, in a televised briefing Monday afternoon. It is unclear whether the killed gunman was included in the 12 fatalities.
The police believed that two other possible gunmen -- a white man and a black man, both in military-style clothing -- were still on the loose, said Lanier, who described that the black male suspect wears an olive-colored military uniform and the white male suspect wears a tan naval uniform.
However, the police department later ruled out the white male as a suspect or person of interest on its Twitter account and welcomed the public who have any suspect information to call the police and the FBI.
District of Columbia Mayor Vincent Gray described the shooting as an isolated incident, and said that the motive and the number of the shooters remained unclear.
Janis Orlowski, chief medical officer of Washington Hospital Center, said the hospital has received three people wounded in the shooting, including a D.C. Washington Metropolitan police officer.
The incident happened at 8:20 a.m. EDT (1320 GMT) when at least a shooter opened fires inside a building at the Washington Navy Yard that serves as the Naval Sea Systems Command Headquarters, the U.S. Navy said on Twitter.
Both U.S. President Barack Obama and Defense Secretary Chuck Hagel have been briefed about the updates of the incident.
Speaking before a televised speech on the fifth anniversary of the financial crisis at the White House, Obama condemned Monday's shooting and sent his thoughts and prayers to the victims and their families.
"We still don't know all the facts. But we do know that several people have been shot, and some have been killed. So we are confronting yet another mass shooting," said Obama, vowing to investigate the incident thoroughly and hold those behind the tragedy responsible.
Pentagon press secretary George Little said, "Everyone here at the Department of Defense is saddened by the incident at the Washington Navy Yard this morning ... Our thoughts and prayers are with the victims."
The Senate also went to recess in light of the attack until Tuesday morning, Senate Majority Leader Harry Reid said Monday afternoon.
At least six schools in Washington D.C. were closed in the wake of the shooting incident.