The man in custody for allegedly killing 12 people at the screening of the latest Batman movie in Aurora, Colorado told authorities after the shooting that he “was The Joker,” NYPD police commissioner Ray Kelly said today.

Kelly told reporters the suspect, identified by federal officials as 24-year-old James Holmes, had dyed his hair like The Joker. The Joker is a well-known villain in the fictional Batman universe. The attack took place at a screening of “The Dark Knight Rises,” the final movie in a Batman trilogy, following “The Dark Knight” in which The Joker was the principal villain.

Two federal law enforcement officials confirmed the details of The Joker costume to ABC News. Police said the weapons used in the massacre include a military-style AR-15 assault rifle, a shotgun and two handguns.