Police in the United States say at least 12 people have died in a shooting rampage at a U.S. Navy base in Washington, D.C.
Washington Police Chief Cathy Lanier said one suspected shooter was among the dead. She said the motive in the September 16 shooting is unknown.
Police were looking for two other suspected assailants believed to be at large. Both were wearing military-style clothing.
At a press conference, U.S. President Barack Obama vowed the perpetrators would be caught and brought to justice for the attack, which took place at the Naval Sea Systems Command Headquarters building at the Washington Navy Yard, located less than five kilometers from the White House.
"As this investigation moves forward, we will do everything in our power to make sure whoever carried out this cowardly act is held responsible," Obama said.
Washington residents were told to stay in their homes and out of the area as the police hunt continued.
Security was also tightened at the U.S. Capitol and other federal buildings.
Police officers and agents from the FBI and other government agencies were all involved in the hunt for the two suspects.
The Naval Sea Systems Command, which employs some 3,000 people, builds and purchases U.S. warships and combat systems.
It is the oldest shore facility of the U.S. Navy.
Based on reporting by Reuters, AP, and BBC