The Cannon Group, Inc. wasn't pleased with Writer and Director Mark Buntzman's original cut of the film, so they had noted film doctor William Sachs do extensive re-shoots in Los Angeles to make the movie better. Also, a garbage truck from New York City had to be driven cross country to Los Angeles for the re-shoots because New York City garbage trucks are made out of steel, while ones from Los Angeles are made out of fiberglass.
Scenes in which John wears a fireproof mask and burns down gang members with a flamethrower were not in the original cut of the movie. They were added during re-shoots, and were filmed with the stunt double of Robert Ginty. Originally, the only scene where John used the flamethrower to kill gang members was in the end when he burned the last few after he already killed most of the others with weapons from the garbage truck. The shot of John taking his mask off in the end after X dies, is actually an outtake edited from this scene, which is why the scene cuts abruptly when he starts taking the mask off. According to an interview from the time when the movie was released, Ginty hated the way the movie was cut down and re-edited by the studio.
Although composers of the score did cut about twenty records for the soundtrack album, it was never released.
The prep time prior to the shooting of this movie was only one and a half weeks.