FBI releases surveillance video of Washington Navy Yard suspect

After Aaron Alexis entered the Washington Navy Yard and killed 12 people before being shot himself, the FBI began a full investigation into his actions.

On Wednesday, they released some of their findings. On the guns used in the tragic shooting, Alexis etched these words: "End to the torment." "Not what y'all say." "Better off this way."

The FBI says he purchased a Remington 870 shotgun and ammo at a gun shop in Northern Virginia on September 14th. Two days later, he pulled his car into the Navy Yard, armed with the gun.

Shortly after he arrived, the FBI says Alexis used the Remington 870 shotgun and a Beretta handgun he obtained during the course of his shooting to kill 12 victims and injure four others before he was shot and killed by law enforcement officers.

Click play to watch the video. Click here to watch it on YouTube.

The FBI released this timeline of the events:

-- 7:53 a.m. - Alexis' rental car, a blue Toyota Prius with New York plates, entered Parking Garage #28 at the Washington Navy Yard, located directly across from Building #197.

-- 8:08 a.m. - Alexis exited Parking Garage #28 on foot carrying a backpack. Alexis entered Building #197 and proceeded to the elevator.

-- 8:09 a.m. - Alexis exited the elevator on the fourth floor and entered the men's bathroom carrying a backpack and a clipboard.

-- 8:15 a.m. - Alexis crossed the hallway into the 4 West area of Building #197 with shotgun, but without the backpack or a clipboard.

-- 8:16 a.m. - Alexis shot the first victim in the 4 West area of Building #197.

-- 8:17 a.m. - First 911 call is received from the fourth floor of Building #197.

-- 8:20 a.m. - Alexis left the fourth floor using the stairs and entered the third floor.

-- 8:28 a.m. - Alexis appeared on the first floor.

-- 8:57 a.m. - Alexis returned to the third floor.

-- 9:25 a.m. - Law enforcement shoot and kill Alexis on the third floor.