(AP Photo/FBI)
(AP Photo/FBI)

Chilling details released about what likely led a military contractor to kill a dozen co-workers at the Washington Navy Yard.

FOX News Radio's Jared Halpern reports from Washington:

(AP Photo/FBI)
(AP Photo/FBI)

Security video captures 34-year-old Aaron Alexis pulling into a parking garage a little before 8am. Later, he calmly walks into Building 197, a backpack around his shoulder.

Alexis is then seen armed with a Remington 870 shotgun, the barrel sawed off. Alexis stalks the halls as if in a combat zone, ducking behind corners and looking for victims.

The FBI concluding Alexis believed he was being controlled by extremely low frequency radio waves. "My ELF weapon" among the etchings made on his shotgun.

In Washington, Jared Halpern, FOX News Radio.

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