Washington, D.C. Mayor, Vincent Gray said late Monday that a motive for the mass shooting at the Navy Sea Systems Command Headquarters has not yet been established. Mayor Gray told reporters that terrorism has not been ruled out.
"We don't have any reason to think that at this stage." Gray said. However, Mayor Gray added that the possibility of terrorism had not been ruled out.
Federal, state, and local law enforcement agencies searched feverishly for a possible second gunman following Monday morning's shooting at a Washington D.C. Naval yard. During a late morning press briefing, Washington, D.C. Metropolitan Police Chief, Cathy Lanier said one or two possible gunman remained at large.
FBI investigators concluded late Monday that the suspected gunman acted alone.
The suspect, identified as Aaron Alexis, 34 years old, was working as a Navy IT contractor from Fort Worth, Texas was staying at a Washington, D.C. hotel.
CNN is reporting that Monday may have been Alexis' first day on the job working for the Navy subcontractor.
Alexis, armed with an AR-15, a rifle and a semi automatic glock when he opened fire killing 12 innocent people before police killed him. Three other victims are being treated at a local Washington D.C. hospital.
Alexis, a Navy reservist from 2007 to 2011, was discharged from the Navy after several incidents of misconduct. Many security experts are questioning how Alexis was able to gain security clearance from the military contractor.
According to public records, Aaron Alexis was arrested in Fort Worth, Texas in September 2010 after firing a bullet into a neighbor's apartment. The round apparently first traveled through the female neighbor's floor and through the ceiling.
Monday's mass shooting is the deadliest shooting at a U.S. military base on American soil since the Fort Hood, Texas Army base terrorist attack in 2009 that killed 13 and wounded 32 others.
On August 28, U.S. Army Maj. Nidal Nasan was sentenced to death by a military jury for the 2009 Fort Hood massacre, the deadliest attack at a U.S. military base in the nation's history.
The FBI Washington, D.C. Field Office is asking for the public's help in establishing a possible motive for Monday's shooting. The following is posted on the FBI official website:
"Aaron Alexis, deceased, is believed to be responsible for the shootings at the Washington Navy Yard, in the Southeast area of Washington, DC, around 8:20 a.m. on September 16, 2013. The FBI is asking for the public's assistance with any information regarding Alexis. If you have any information concerning this individual, please contact the FBI's Washington, DC Field Office at 202/278-2000 or 1-800-CALL-FBI."