Arlington Road (1999)

Directed by Mark Pellington, Arlington Road stars Jeff Bridges as a traumatized professor who becomes convinced that his seemingly ordinary neighbor is involved in domestic terrorism. As suspicion deepens, paranoia, surveillance, and moral certainty collide. The film builds toward a bleak conclusion that challenges assumptions about truth, trust, and security.

Från IMDB:
A man begins to suspect his neighbors are not what they appear to be and their secrets could be deadly.