The FBI released surveillance video of Aaron Alexis preparing for his Navy Yard massacre on Wednesday, along with pictures of the shotgun used in the attack and an electronic note left by Alexis.

In the video, Alexis arrives at the Navy Yard, walks into the building and then gets out his shotgun. Alexis reportedly wrote that he was subjected to an “ultra low frequency attack” that led him to commit the mass shooting, killing 12 and wounding four on Sept. 16.

“An ultra low frequency attack is what I’ve been subject to for the last three months, and to be perfectly honest, that is what has driven me to this,” he wrote.

The FBI believes that Alexis was not looking to hurt specific individuals, and that he understood that he would most probably die as a result of the shootings.

“There are indicators that Alexis was prepared to die during the attack and that he accepted death as the inevitable consequence of his actions… There is no indication to date that Alexis was targeting specific individuals,” Valerie Parlave, Assistant Director of the FBI’s Washington field office, said.

On his shotgun, Alexis had etched two messages. The first reads, “Better off this way,” and the second, “My ELF weapon” is believed to be a direct reference to the ‘low frequency’ attack Alexis alluded to in his note.

Reports speculate that Alexis was paranoid and had a history of fearing harm from microwaves and frequencies of light. In August, Alexis was approached by police in his Rhode Island hotel room and told them that he was being driven mad by the voices in his head and microwaves.

“At this point, I can confirm that there are multiple indicators that Alexis held a delusional belief that he was being controlled or influenced by extremely low frequency, or ELF, electromagnetic waves,” Parlave confirmed.

In addition to the ongoing FBI investigation into the shooting, the Pentagon is looking into how Alexis came to be hired and cleared to work at the Naval facility.

“We need to know how an employee was able to bring a weapon and ammunition onto a defense installation, and how warning flags were missed, ignored, or not addressed in a timely manner,” Ashton Carter, a Pentagon official, said.

Olivia Truffaut-Wong

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