A week before “Joker” hits the big screen, movie theaters around the country are banning masks and costumes at showings amid concerns about its violent theme and after the families of those killed in a 2012 mass shooting at a Colorado theater expressed alarm.

Landmark Theaters, a Los Angeles-based chain with more than 50 venues nationwide, told Reuters that “no masks, painted faces or costumes” will be allowed in its theaters. Earlier this week, AMC Theatres, the biggest movie-theater chain in the country, issued a reminder that it will not allow customers to obscure their faces, though they are free to wear costumes.

“Guests are welcome to come dressed in costume, but we do not permit masks, face paint or any object that conceals the face,” the Kansas-based company said in a widely reported statement this week. “AMC does not permit weapons or items that would make other guests feel uncomfortable or detract from the moviegoing experience.”

The film starring Joaquin Phoenix has been both heralded and criticized for its portrayal of a failing clown who unravels, becoming a mass murderer and a sort of dark folk hero. Some see it as a close examination of the forces that can push a person to commit such atrocities; others say it lionizes the mass violence that’s become increasingly common in recent years.

In 2012, a heavily armed man murdered 12 people and wounded 70 during a screening of “The Dark Knight Rises” in Aurora, Colo., where many audience members were in costume. Police said James Holmes had dyed his hair orange-red so he would look like the Joker, the Batman villain. He was later convicted on 165 charges and is serving a life sentence.

The Century 16 Theater where the attack occurred will not be screening “Joker,” and earlier this week, relatives of the massacre’s victims raised concerns about the film in a letter to the studio behind it, Warner Bros. The letter called on Warner to stop supporting political candidates who accept money from the National Rifle Association and to lobby for gun reform.

The studio, in turn, extended its sympathy to victims of gun violence and said it had recently joined the call for bipartisan gun-reform legislation. But they also asserted that “Joker” was in no way an “endorsement of real-world violence of any kind.”

“At the same time, Warner Bros. believes that one of the functions of storytelling is to provoke difficult conversations around complex issues,” the studio said in a statement. “It is not the intention of the film, the filmmakers or the studio to hold this character up as a hero."

Phoenix recently walked out of an interview with the Telegraph after being pressed about whether the film could inspire real-world acts of violence. When he returned, Phoenix said he had panicked because he hadn’t considered the question before. During the rest of the interview, which has since gone viral, he never explicitly answered the question.

The FBI has told local law-enforcement agencies to watch for troubling online posts related to the movie. And earlier this week, a memo at a U.S. Army base in Oklahoma warned of “disturbing” online chatter about a potential threat and urged soldiers to be cautious at screenings, according to news reports. However, Christopher Grey, chief of public affairs for the U.S. Army Criminal Investigation Command, told the Associated Press that officials are “not aware of any information indicating a specific, credible threat to a particular location or venue.”