FBI says Navy Yard killer believed his mind was being controlled

The FBI has released chilling surveillance video and photos of Navy Yard shooter Aaron Alexis, saying he believed electromagnetic waves had been controlling him for months before the rampage that killed 12 people.

There were no signs that Alexis, 34, was targeting anybody in the September 16 shooting 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 during a news conference on Wednesday.

Surveillance video released by the FBI showed Alexis driving a rented blue Toyota Prius into a Navy Yard parking garage shortly before 8am. Carrying a backpack, he then entered the Naval Sea Systems Command building, site of the shootings, through a door.

The brief video also shows Alexis, armed with a Remington shotgun and wearing dark clothing, descending a stairway and walking along corridors in a crouch position, weapon held at the ready.

People can be glimpsed at the end of one corridor. Alexis peeks around corners and, at one point, aims the shotgun into a room but does not fire.

Parlave said Alexis, a government technology contractor, had in his possession the shotgun, which had a sawed-off barrel and stock, and a pistol he obtained during the shooting.