DENVER — The Colorado movie theater complex that was the scene of a gunman’s massacre this month didn’t have any uniformed security guards on duty the night of the shooting, even though other theaters operated by the same company did provide such protection for the busy premiere of the Batman film “The Dark Knight Rises.”

It’s impossible to know whether guards — often off-duty police officers — at the Aurora Century 16 would have spotted the suspected gunman, James Holmes, and thwarted the attack that left 12 moviegoers dead and dozens wounded on July 20.

Officers hired as guards are generally armed and usually spend their time roaming the complex, checking bags or dealing with minor disputes.

Cinemark provided off-duty police guards at the Aurora theater on busy Friday and Saturday nights. As for other nights of the week, theater operators decide on a case-by-case basis whether to hire security, depending on the likelihood of trouble. The attack came early Friday, shortly after the midnight screening of the Batman film began.

Larry Lowak, whose son Brent was among the wounded, said security personnel on the scene possibly could have stopped the gunman, and he was dismayed to learn that guards weren’t on hand.

“If you bring in security on Friday or Saturday, you sure as hell want to bring it in for this particular function,” Lowak said.

Plano, Texas-based Cinemark, which operates the Aurora theater, declined to explain why guards weren’t provided in Aurora that night and declined to discuss safety policies in general.

Through interviews with police officers and officials outside the theater company, The Associated Press was able to identify places around the country that did use armed security workers for the July 19-20 Batman showings — including places like Beaumont, Texas; Lake Charles, La., and Tupelo, Miss.

Some other locations, including a Cinema Century 16 theater in the western Denver suburb of Lakewood, did not have security.

Aurora Police Chief Dan Oates has said that the Cinemark in Aurora normally uses off-duty officers to provide security on weekend nights but did not have any working for the July 19 showings that went into the next morning. The theater does not have an unusually high record of complaints or crimes, police Sgt. Cassidee Carlson said.

In Moosic, Pa., Cinemark has worked for years with off-duty officers from the local police department — typically on Fridays and Saturdays — and authorities said they were asked to provide two officers on July 19 because the midnight showing was likely to be a major event.

“If they’re expecting large crowds, they call our department for additional police presence,” said Moosic Borough Police Officer James Giehl.

Two major multiplexes in Amarillo, Texas, including one Cinemark facility, also ensured that off-duty uniformed police officers were present for the first screenings of the Batman film. Amarillo Police Cpl. Jerry Neufeld said that the off-duty officers work in pairs; the town’s theaters made a point of asking for them on the busy opening night.

There were no incidents at the screenings, and Neufeld said he heard that people were, as always, happy to see people there to deal with any dangers.

“When they’re there, they’re visible, people see them and people come in and say, ‘hey man, we’re glad you’re here,”’ Neufeld said. “It gives people a sense of calm.”

The Aurora shooting has stirred discussion about appropriate security precautions at gathering places commonly considered safe from the cares and worries of the outside world. Experts say that security at public venues has increased substantially over the past decade, but they also note that it’s impossible to maintain perfect safety at all times.

Officials have said the Aurora shooting suspect bought a ticket to the midnight showing and went into the theater as part of the crowd. A federal law enforcement official said suspect Holmes is believed to have propped open an exit door in the theater as the movie was playing, donned protective ballistic gear, re-entered about a half-hour into the film and opened fire.

Aurora police said the suspect tossed two gas canisters into the crowd and had an AR-15 assault rifle, a shotgun, and two .40-caliber Glock handguns.

Some theaters have added security guards for all nights of the week since the shooting, and police departments around the country have also conducted extra patrols that focus to movie theaters, though it’s not clear if those shifts will be permanent. AMC Theatres has barred people from wearing masks or bringing fake weapons inside its buildings.

Many theaters, including the Cinemark in Aurora, prohibit patrons from bringing in their concealed weapons they use for personal protection.

That irks people like Dudley Brown, executive director of Rocky Mountain Gun Owners, who said that he has refused to go to Aurora theater because of that ban.

“What could have stopped this is law-abiding citizens being allowed to carry,” Brown insisted.

Lowak, the father of the shooting survivor, also said he believes people carrying concealed weapons might have helped limit the bloodshed.

But Hubert Williams, former head of the Newark police department and president of the Police Foundation, said that the idea that average citizens with guns could keep a theater safe only makes sense “on a piece of paper.”

“Reality is much more complicated. What if you pull a gun out, take aim and someone else thinks you’re the shooter?” he asked. “Would you stand up against an AR-15, AK-47 military-style assault weapon? Give me a break.”