In addition to releasing surveillance video of Navy Yard shooter Aaron Alexis creeping through hallways during his attack, the FBI revealed that Alexis left a note of sorts. “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," said the message found either on his laptop or another electronic device, reports USA Today. It meshes with his complaint to police a month before the shooting that assailants were attacking him with a "microwave machine."
It also seems to explain a message he had carved or scratched onto his gun calling it his "ELF weapon," an apparent reference to "extremely low frequency" waves. Other messages included "End to the torment!" “not what y’all say," and “better off this way." FBI official Valerie Parlave said it was clear from other writings that Alexis planned to die during his siege, reports the Washington Post. She added that on the Friday before the shooting spree, Alexis had discussed some kind of a performance issue with his boss or bosses, but that it didn't appear he targeted anyone from his job.