The early Friday attack in Aurora, Colo., at a midnight screening of the new Batman movie, "The Dark Knight Rises," left 12 people dead and dozens wounded. Authorities say the gunman apparently slipped out through an emergency exit to arm himself, then re-entered that way and opened fire on the startled audience.
The attack had a chilling effect on some ticketholders who had been eagerly awaiting what had been billed as the summer's hottest movie.
"I'm just going to keep my eyes and ears open for anything strange," 27-year-old Charlotte Kimbrell, of Belleville, Ill., said before a screening of "Dark Knight" at a theatre in nearby O'Fallon. "I'll probably be sitting all the way in back today, away from the exit doors."
It was in the back of some baseball fans' minds Friday, as well.
"I think paranoia takes over after something like that and something like today, but I think for the most part, all they can do is check your bags and hope that you're not crazy," said David Karney, of Quincy, Mich., who watched the Detroit Tigers host the Chicago White Sox. "At the end of the day, if you're crazy and want to do something, you're going to do it."
The angst is understandable after the attack, which was one of the deadliest mass shootings in recent U.S. history. But security experts say changes made at ballparks, theatres and concert venues after the Sept. 11, 2001, terrorist attacks have gone a long way toward making them safer.
"The problem is security is never 100 per cent," said Richard Sem, a longtime security management executive from Wisconsin who is now a consultant. "We look at what's reasonable, practical. You don't necessarily need Fort Knox to go to a Sunday afternoon baseball game."
A decade after the terrorist attacks, at ballparks and concerts, bag checks are now common when entering a venue. Sometimes, there are metal detector wand scans at sporting events. Some movie theatres already have random bag checks. But experts say that it can be a difficult choice to decide where to install additional extra measures, and note that it's no guarantee a patron will be safer with them in place.
"Are we going to put in security that might not work at every movie theatre, at every mall?" asked Derek Catsam, a history professor at the University of Texas of the Permian who studies and writes about stadium security issues. "Think of all the places you go during the day where you stand in line or are stuck in crowds. This could happen at any of those places."
At Busch Stadium in St. Louis, where the Cardinals were hosting the rival Chicago Cubs for three sold-out weekend games, security officials were on alert Friday.
"We're concerned, we're certainly saddened and we'll be extra vigilant in our regular security," said Joe Abernathy, vice-president of stadium operations.
Abernathy said there were no major security changes planned because the team feels it's already doing everything it can to keep fans safe. Police officers man stadium entrances, and there are nearly 150 security cameras at the ballpark. All bags are checked at the entrance. And costumes, in which someone might hide a weapon, aren't allowed, not even masks.
Fans have generally embraced the changes. Butch Cox, a fan at Friday's Cardinals-Cubs game, said, "If they wanted to strip search me, I could care less. If it's for the better, I'm all for it."
Richard Ballentine, of Valrico, Fla., who watched the Tampa Bay Rays host the Seattle Mariners on Friday, said he was worried that the Colorado attack would lead to airport-style metal detectors at movie theatres and stadiums.
"I'm actually of the opinion that most of those checks are a waste of time. They're reactive instead of being proactive," Ballentine said. "... The truth is terrorists will look at the things that we're doing to try to provide security and they'll look for other places that are weak spots, and they'll just adapt."
Brian McCarthy, of the National Football League, said security procedures are under constant review and are sometimes adjusted.
Last season, the league provided handheld metal detectors to its 32 teams — part of a massive security effort at NFL games and one fans don't seem to mind because they're less intrusive than pat-downs, said Bob Calderon, who oversees public safety at the Edward Jones Dome in St. Louis.
"They'd rather be safe than sorry," he said. "We try to reach a happy medium."
Officials at St. Louis-based Wehrenberg Theatres Inc. met before dawn Friday to consider what to do after the shooting. The chain manages 15 cinemas in Missouri, Illinois, Minnesota and Iowa. But they noted that security measures were already in place. Wehrenberg's vice-president of marketing, Kelly Hoskins, said the chain already uses off-duty uniformed and civilian-dressed police and does random checks of handbags for movie-goers.
"Sometimes you don't want it to feel like a police state," Hoskins said. "You don't want to increase security to an uncomfortable level."
Associated Press journalists John Affleck and Barry Wilner in New York, Jay Reeves in Birmingham, Ala.; Fred Goodall in St. Petersburg, Fla., Jim Suhr in O'Fallon, Ill, and RB Fallstrom in St. Louis contributed to this report.