Dramatic, just-released video of crazed killer Aaron Alexis stalking victims inside the Washington Navy Yard has just been released .

The chilling images show Alexis arriving at the Navy Yard in a blue Toyota Prius. The deranged killer is seen casually walking into the building with a backpack.

He leaves the backpack in a men's room stall, then stalks the corridors with his shotgun. He runs from floor to floor hunting for victims. He checks a door and readies to shoot, but no one is there.

Then, he takes cover with workers nearby at the end of the corridor.

The FBI also released photos of his shotgun, with the words "Better Off This Way," "My Elf Weapon" and "An End To The Torment" crudely scratched on it.

It's a shocking surveillance video of a man who took 12 innocent lives before being shot down himself.