The FBI released video Wednesday showing Navy Yard shooter Aaron Alexis entering Building #197 and lurking around the hallways with a Remington 870 shotgun in hand.
The video was taken from closed circuit video footage from the building.
In about 90 minutes on Sept. 16, Alexis shot and killed 12 victims and wounded four more in Building #197.
The FBI also released the most detailed timeline to date of what happened at the Navy Yard.
Security camera footage shows Aaron Alexis drove to Parking Garage #28 at the Navy Yard that Monday morning in a blue Toyota Prius with New York plates. He walked across the street into Building #197 and took the elevator to the fourth floor, carrying a backpack.
He then went into a restroom with the backpack and came out with a shotgun, later identified by the FBI as a sawed-off Remington 870.
At 8:16 a.m., Alexis shot his first victim, and at 8:20, he moved from the fourth floor to the third floor by taking the stairs.
Alexis appeared on the first floor at 8:28 and moved back to the third floor at 8:57, where he was shot and killed roughly thirty minutes later by law enforcement officials at 9:25.
An investigation of Alexis’s history found that he had been living in a Residence Inn in Southwest D.C. at the time of the shooting.