Watching the footage, nearly six months later, is a kind of compulsive ghost-hunting. In the antiseptic stare of the surveillance camera, even the most ordinary interactions are deformed, made weird only by what we know now. It is unnerving because it ends in the deadliest mass shooting in modern American history. It is unnerving because even with his every movement laid out, the grotesquely composed protagonist of this film gives away nothing.

The faces of hotel guests and staff are blurred to preserve their privacy, reducing them to smudges that crisscross the screen at random. Mr. Paddock is the only person who appears throughout, the Waldo whose distinctive frame and faintly lopsided gait our eyes quickly learn to seek out in every frame. The clips begin when he appears and end after he leaves. The other people are little more than a backdrop.

Except that some of them may become his victims. And some are already his unwitting accomplices.