Navy Yard shooter Aaron Alexis believed he was being controlled by electromagnetic waves in the months before he killed 12 people at a Washington base on September 16, an FBI official said on Wednesday.
There are no indications that Alexis, 34, was targeting anybody in the rampage at the Navy Yard in southeast Washington, said Valerie Parlave, the FBI assistant director in charge of the Washington field office.
"We have found relevant communications on his electronic media which referenced the delusional belief that he was being controlled or influenced by extremely low-frequency electromagnetic waves for the past three months," Parlave said.
Alexis, a government technology contractor, acted alone and was killed by police on the third floor of the Yard's Naval Sea Systems Command headquarters, after exchanging fire with officers for an hour, she said.
The shooting spree and the question of how Alexis got security clearance to enter the base have prompted calls for a review of government vetting of private contractors.