A shooting at the midnight showing of "The Dark Knight Rises," in Aurora, Colo. by a lone gunman left 12 people dead and 58 others injured.
The LAPD said officers have been sent to major venues where "The Dark Knight Rises" is playing. The L.A. County Sheriff's Department also said residents will see increased patrols by deputies.
"I am outraged by the cowardly attack on innocent movie patrons in Colorado last night," said LAPD Chief Charlie Beck in a statement. "Since Los Angeles is the entertainment capital of the world, it is important that we all remain vigilant and do everything we can to prevent incidents like this from occurring in our communities."
ArcLight Cinemas said it is adding more officers at ArcLight and Pacific theaters. ArcLight and AMC said it will still allow moviegoers to enter theaters in costumes, but prohibits masks, face paint and props.
"Movie going is part of our social fabric and this senseless act shakes us to our core," AMC said in a statement. "We are taking necessary precautions to ensure our guests who wish to enjoy a movie this weekend can do so with as much peace of mind as possible in these circumstances."
Security consultant Joe Petrillo said he believes the suspect had carefully planned his actions for quite a long time because it took time to get the ammunition and weapons.
"Always worry about copycats, always, because the copycats are usually not as sophisticated as he was, they don't usually have it planned out, but they'll go to big areas, areas of mass people, and they'll commit some acts of violence," Petrillo said.
Even after word spread of the chaotic scene in Colorado, people in downtown Los Angeles continued to line up to buy tickets for the movie.
"'The Dark Knight Rises' outweighs everything else, but my heart goes out to the victims out there," said moviegoer Tiny Te Vu.
They did, however, admit that safety while watching the movie is a major concern now.
Regal Cinemas said in a statement, "The security and safety of our guests and staff is always our number one priority. As is our custom, we continue to monitor the situation and adjust our security needs as necessary."
Police say 24-year-old James Holmes barged into a packed auditorium at the Century 16 Movie Theaters at the Aurora Town Center, set off gas canisters and began shooting into the crowd - picking off people who tried to flee.
Anyone who sees suspicious activity is urged to call the LAPD at (877) LAPD-24-7, or LA Crime Stoppers at (800) 222-TIPS.