US authorities probing the shooting spree at Washington's Navy Yard, which left 13 people dead and eight injured, have said that a lone gunman carried out the killings.

Authorities said military contractor Aaron Alexis, 34, of Texas, launched the attack on Monday inside a building at the US Navy complex, spraying gunfire on office workers in the cafeteria and in the hallway at the heavily secured installation.

Al Jazeera's Kimberly Halkett reports.