Partially shot with the same 35mm hand-crank camera Tony Scott used on Man on Fire and Domino.
Thomas Berkson is a reference to David Berkowitz the infamous "Son of Sam" killer who later became a born-again Christian in prison.
Over 10 different types of cameras were used to create the various looks within the film.
90% of the gore are done by practical effects.
There is a post-credits scene.