Aaron Alexis, the man who went on the deadly shooting rampage at the Washington Navy Yard, was under the "delusional belief that he was being controlled or influenced by electro-magnetic waves," the FBI's Valerie Parlave said Wednesday.
Parlave, assistant director in charge of the FBI Washington Field Office, said Alexis acted alone and there was no evidence he was targeting particular people.
Alexis, who was 34, went on the rampage September 16, killing 12 people and wounded several others. Chilling video released Wednesday shows Alexis running through hallways with a sawed-off shotgun. He also gained access to and used a Beretta pistol during the shooting.