Navy Yard death toll reaches 12 09/16/13 02:48 PMUpdated 10/07/13 06:18 PM facebook twitter like save share group discuss By Steve Benen Following up on earlier item, new information continues to become available from D.C.A man brandishing an assault rifle, shotgun and handgun opened fire Monday inside a building at the Washington Navy Yard. The city police chief said 12 people were killed.SWAT officers swarmed the building, the headquarters of the Naval Sea Systems Command, and a shooter there was killed, sources told NBC News. Law enforcement officials identified the gunman to NBC News as Aaron Alexis, 34, originally of Fort Worth, Texas. They said he recently began working as a civilian contractor.D.C. Police Chief Cathy Lanier added that there are two other “potential” accomplices who have not yet been located*.Lanier said one of the other potential shooters was a white male in his 40s or 50s dressed in a khaki or tan short-sleeved Naval-style uniform with a beret last seen between 8:35 and 8:40 a.m. The man was seen carrying a handgun, she said. A third potential shooter was described as a 50-year-old black man with graying sideburns dressed in olive drab military style clothes and weighing about 180 pounds who may have been carrying a long gun.“There is no information to believe either of those folks are military personnel, but we do have information that those people are wearing military-style uniforms,” Lanier said.With 12 fatalities, and an undetermined number of injuries, this morning’s mass shooting is the deadliest in the U.S. since the massacre at Sandy Hook Elementary last December, and the worst at a military installation since 13 people were killed at Fort Hood in 2009.* Update: As I was typing this, the D.C. Police tweeted, “The white male in the tan outfit has been identified and is not a suspect or person of interest.” Explore:Gun Violence, Guns and Society facebook twitter like save share group discuss More Like This Race, Women 'MHP' Syllabus: November 10 Election 2016, Money in Politics 'MHP' Syllabus: November 16 Race, Middle East 'MHP' Syllabus: November 17 Guns Mothers plea: Stop 'Stand Your Ground'