(RNN) - The FBI released surveillance footage Wednesday showing Aaron Alexis at the Washington Navy Yard moments before the shooting that claimed 12 lives.
An investigation into why Alexis opened fire on a crowd of people at the Naval complex has been ongoing, according to Valerie Parlave, head of the FBI's Washington, DC, field office. She said the shooter did not appear to have any specific targets.
Alexis had the phrases "not what yall say," "end to the torment" and "my ELF weapon" etched into the shotgun. Parlave said he believed something was attempting to control him with extremely low frequency, or ELF, electromagnetic waves.
The investigation indicates that Alexis "was prepared to die during the attack and that he accepted death as the inevitable consequence of his actions," Parlave said during a press conference Wednesday.
According to a FBI news release, a document retrieved from electronic media showed Alexis said, "Ultra low frequency attack is what I've been subject to for the last 3 months, and to be perfectly honest that is what has driven me to this."
The 31-second video shows Alexis driving a blue Toyota Prius and then entering a building with a backpack slung over his left shoulder. In the next clip, he can be seen walking down a hallway with the shotgun in hand.
He then runs down a flight of stairs, goes through a door and moves to another hallway where people can be seen walking in the distance.
Officials said Alexis came to Washington, DC, on Aug. 25 and had been staying in hotels in the days before the shooting. As a former Navy reservist and a government subcontractor, he had credentials to gain access to the military base.
Alexis entered the Naval Sea Systems Command building Sept. 16 and opened fire on a crowd of people, killing 12 and injuring eight others. He was killed in a confrontation with members of law enforcement at the scene.
Among the dead were Michael Arnold, 59; Sylvia Frasier, 53; Kenneth Proctor, 46; and Kathleen Gaarde, 63. Also killed were John Roger Johnson, 73; Vishnu Pandit, 61; Frank Kohler, 50; Martin Bodrog, 54; Arthur Daniels, 51; Mary Francis Knight, 51; Gerald L. Read, 58; and Richard Michael Ridgell, 52.
None of them were military personnel.
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