(Image Credit: ABC News)

Less than one day after he escaped the chaos and carnage of the Aurora, Colo., theater shooting, lifelong Batman fan Justin Davis was back at the movies with a sense of purpose.

Davis, 16, was accompanied by his brother and a friend to a screening of "The Dark Knight Rises" at a different Colorado movie theater.

"I just want to finish it, and for all those men, women and children that didn't get to finish it, I want to finish it for them," he said.

Shortly after midnight on Friday, a shooter opened fire in a packed theater in Aurora, killing 12 people and injuring 58 in the nation's largest mass shooting.

New York City, Chicago and Los Angeles are among the major cities where police departments are ramping up security at theaters in response to Friday's shooting.

"We are doing that to address the potential of a copycat event," said New York Police Commissioner Raymond Kelly.

No significant drop in attendance has been reported around the country, although some movie goers said they felt on edge.

"When we first arrived, I was like, 'Hey maybe we should sit closer to the exit,'" said Michael Scheno, who saw the movie in New York City.

AMC Theaters announced Friday it had banned costumes from its theaters to provide an element of increased security.

Warner Brothers will not report "The Dark Knight Rises" box office results this weekend "out of respect for the victims and their families," according to a statement. Box office numbers will instead be released on Monday.

ABC News' Clayton Sandell and John Schriffen contributed to this report.