I wonder if his first name is "Gary"?
"Folie à Deux" is the nineteenth episode of the fifth season of American science fiction television series The X-Files. It was written by Vince Gilligan and directed by Kim Manners. ...This episode of "The X Files" was about a seemingly normal man who was actually an alien monster who "hides in the light" and preys on those around him, turning them into zombies under his control.
The only one who can see the monster for who and what he really is Mr. Gary Lambert.
Lambert is eventually shot down by the FBI.