The U.S. Army has issued a warning to its fellow service members about the possibility of a mass shooter at screenings of the upcoming 'Joker,' film. The film has already drawn concern from families of those killed during the 2012 mass shooting in Colorado. The warning comes after the FBI alerted the Army of social media posts that encourage shootings during the premiere.

The Army issued the warning on September 18 and reminded their forces to be aware of their surroundings and find the closest escape routes when they enter theaters. They also say, if you happen to be face-to-face with the shooter, fight with whatever you have on hand.

If you are trapped in the area, they must "shelter in place and stay quiet."

US Military received warnings from FBI

The Army's alert comes from a Federal Bureau of Investigation bulletin, who were monitoring posts, but did not have any knowledge of specific plots or even suspects. The FBI bulletin was "For Official Use Only," and was sent more as a precautionary measure.

The Army's Criminal Investigation division said the Army has received credible intelligence from a Texas law enforcement agency, regarding serious chatter on the dark web over the targeting of a movie theater during next week's "Joker" release. The Army says this warning is just an effort to keep their forces prepared when it comes to personal safety.

Social media posts from 'incels' have Army and FBI concerned about potential attacks

The FBI discovered social media posts from "incels," that created red flags among law enforcement. According to the FBI, "incels" are those who are unable to find a partner even though they desire one. The FBI has said that 2012 shooter James Holmes is a legend among the incels.

The memo says that incels are drawn to the Joker because he is one who pretends to be happy and fights back against bullies. The FBI and Texas law enforcement are still investigating the threats.

'Joker' is the latest chapter in the DC Comics franchise. It tells the origin story of the villain, played by Joaquin Phoenix. Phoenix plays Arthur Fleck, who starts out as a struggling comedian who falls into madness and becomes a mass murderer and inspires those around them to engage in anarchy.

The film caused some serious controversy when its first trailer drop coincided with several mass shootings that took place across the United States, including El Paso and Dayton, Ohio.

Critics point that the film allows "incels" to feel for the main character, where "incels" feel alienated and turn to violent action when they feel like they have been cheated out of what they believe they deserve, including romance and desired physical features.