Police tape off a section of DC around the Navy Yard Monday.

Police tape off a section of DC around the Navy Yard Monday. Jacquelyn Martin/AP

Thirteen Dead, 14 Injured in Mass Shooting at Washington Navy Yard

Dead gunman identified as Aaron Alexis, an IT subcontractor.

Thirteen people were shot and killed at the Washington Navy Yard on Monday morning after a shooter or shooters opened fire inside a headquarters building, and 14 people were injured, authorities confirmed Monday.

The gunman was reported dead at the scene, and has been identified as Aaron Alexis, 34. Alexis was reportedly working as a subcontractor for Hewlett Packard on a major technology project. The Guardian's Spencer Ackerman reports Alexis "served in the U.S. Navy from May 2007 to January 2011, according to Rear Admiral John Kirby, the Navy's chief of information."  Defense officials told CNN he was discharged after a pattern of misconduct. 

All of those killed were civilians, the Navy said Monday night. Personnel were slowly being allowed to leave the base Monday, but as of 8:30 p.m., about 2,000 civilians remained and Navy officials said it could take hours to get everyone home. The Navy Yard will be closed to all but essential personnel on Tuesday. 

Per the Navy's official release, someone entered the Naval Sea Systems Command Headquarters building around 8:20 a.m. Monday morning, where roughly 3,000 people work, and began firing shots. The Metropolitan Police Department, the Military Police and the Capitol Police are assisting with the response. There was a "shelter in place" order while law enforcement agencies entered the building to confront the shooter, who was believed to be barricaded inside a room.

The FBI has taken over the lead in the investigation.

Read more on The Atlantic Wire