Aaron Alexis was under "the delusional belief that he was being controlled or influenced by extremely low frequency electromagnetic waves" before he embarked on a bloody shooting rampage at the Washington Navy Yard, an FBI official said Wednesday.
CNN's Joe Johns reports.
The 34-year-old contractor, who until a few years ago had served in the Navy, spelled out this belief - with the words, "My ELF weapon" - in the sawed-off Remington 870 shotgun he brought into the military facility's Building #197 on the morning of September 16.
"ELF" refers to low-frequency electromagnetic waves, a technology used for submarine communications that conspiracy theorists believe the government employs to monitor and manipulate unsuspecting citizens, the FBI said.
"Ultra low frequency attack is what I've been subject to for the last 3 months," read a message obtained by federal authorities from Alexis's thumb drives, phones and computers. "And to be perfectly honest, that is what has driven me to this."