Warner Bros. announced the rescheduled release Thursday. The film was expected to be reshot and edited. A Warner Bros. spokesman reportedly declined to comment on how the film would be altered.
The film was originally scheduled for a September 7 release. The postponement means "Gangster Squad" won't be eligible for Academy Awards consideration this year, shifting from a plum fall release to a month often considered a dumping ground.
The film stars Ryan Gosling, Emma Stone, Josh Brolin and Sean Penn, and was directed by Ruben Fleischer.
The film's violent trailer was pulled from theaters and the Internet after the early-morning shooting Friday in Aurora, Colorado.
Shot at the famous Grauman's Chinese Theater in Los Angeles, the scene is a centerpiece to the film, meaning reshoots may be extensive.
This is the second time this year a high-profile studio movie has had its release altered by news events.
Twentieth Century Fox's "The Watch," which is out Friday, had its title changed from "Neighborhood Watch" after the Trayvon Martin killing in Florida. The film's trailer and promotional materials were also adjusted to distance the film from the incident.
The Associated Press contributed to this report.