Navy Yard shooting FBI video was released of Aaron Alexis arriving on the scene, gun in hand, moments before he killed 12 people last week.

The FBI said that Alexis believed electromagnetic waves had been controlling him for months before the Navy Yard shooting. This video speaks for itself with what looked like a movie with Alexis going into different rooms and hallways, hiding from the people walking nearby.

In the video released by the FBI, Alexis is armed with a Remington shotgun, wearing dark clothing. Somebody holds the door to him as he goes into the Navy Yard. He sneaks around and at one point points the gun in the direction of a group of people, but does not fire before the deadly shooting.

The video also shows him driving a rented blue Toyota Prius into a Navy Yard parking garage shortly before 8 a.m.

There are no signs that Alexis, 34, was targeting anybody in the September 16 shooting at the Navy Yard in southeast Washington, Valerie Parlave, the FBI assistant director in charge of the Washington field office said at a news conference.

"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 told a news conference.

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. He was killed during an hour-long shootout with police after he already killed 12 civilians himself.