Directed by Todd Phillips, the film stars Joaquin Phoenix as Arthur Fleck, a lonely man suffering from a disorder that makes him an outcast in his society. The psychological thriller, which follows Fleck as he spirals into the depths of his mental illness and becomes the murderous DC Comics villain, has sparked conversation for its realistic gun violence and brutal scenes.

"I want customers to be comfortable in their surroundings," Landmark president-CEO Ted Mundorff tells The Hollywood Reporter, noting Joker's dark themes. Landmark currently has 50 theaters across the nation.

Since the 2012 shooting at a midnight screening of The Dark Knight Rises in Aurora, Colorado, most movie theaters across the country have not allowed customers or employees to wear face masks and face paint or to carry toy weapons. Body costumes, however, have generally been allowed.

To date, the FBI has not alerted the National Association of Theatre Owners of any credible threats regarding Joker's run in theaters.

Regal Cinemas weighed in on Thursday, saying, "We do not believe the content or the existence of any movie is a cause or a signal for violence. Nevertheless, although we do not comment on security protocols implemented by our theaters at any time, patron and employee safety is our foremost concern. In collaboration with NATO, we are in regular contact year-round with law enforcement so we have information to help make whatever security assessments they deem appropriate at all times.”

Earlier this week, AMC Theatres reiterated its ongoing policy regarding costumes: "Guests are welcome to come dressed in costume, but we do not permit masks, face paint or any object that conceals the face. AMC does not permit weapons or items that would make other guests feel uncomfortable or detract from the moviegoing experience."

Joker, which made its premiere at the Venice International Film Festival, is positioning itself to be a major awards player, with particular focus on Phoenix's performance.