A gunman in a gas mask and body armour opened fire at a packed midnight showing of the new "Batman" film in a Denver suburb on Friday, killing 12 people after hurling a gas canister into the crowded multiplex theater.
Armed with an assault rifle, a shotgun and a pistol, he wounded 58 others in the shooting rampage at a screening of "The Dark Knight Rises" at a mall in Aurora, which turned into a chaotic scene of dead or bleeding victims, horrified screams and pleas for help, witnesses said.
Police, who initially said 59 people were hurt, said 30 people remained hospitalized on Friday evening, 11 of them in critical condition.
Officers who arrived on scene within 90 seconds of the first emergency calls quickly took suspect James Eagan Holmes, 24, into custody in a parking lot behind the cinema, where he surrendered without a fight, Aurora Police Chief Dan Oates said.
Holmes, a graduate student who authorities said had his hair dyed red and called himself "the Joker" in a reference to Batman's comic-book nemesis, was due to make his first court appearance on Monday.
Police said Holmes had also booby-trapped his Aurora apartment with what appeared to be sophisticated explosives, creating a potential hazard for law enforcement and bomb squad officers who swarmed to the scene.
Authorities evacuated five nearby buildings and created a perimeter of several blocks as they planned to detonate the suspected explosives with a robot, a fire official said.
Meanwhile, police used dogs to search three buildings in a research complex at Anschutz Medical Campus at the University of Colorado at Denver where Holmes had worked. A university spokeswoman said nothing suspicious was found.
Witnesses at the movie theater told of a horrific scene, with dazed victims bleeding from bullet wounds, spitting up blood and crying for help. Among those taken to hospitals as a precaution was a 3-month-old baby boy.
"I slipped on some blood and landed on a lady. I shook her and said, 'We need to go, get up,' and there was no response, so I presumed she was dead," said Tanner Coon, 17.
"I went toward the exit, waited in the exit for my friends and saw a guy with blood across his face and shoulders, and just got out of the movie theater."
Confusion reigned as shooting broke out during an action scene in the summer blockbuster. The suspect may have blended in with other moviegoers who wore costumes as heroes and villains, and some witnesses said they believed at first that his appearance was a theatrical enhancement to the film.
"It was just straight chaos," said Jennifer Seeger, 25. "Everybody was starting to scream and run at that point. He went straight from here to here with a gun in my face at that point. That rifle was in my face and I honestly didn't know what to think."
The shooting evoked memories of the 1999 massacre at Columbine High School in Littleton, 17 miles from Aurora, where two students opened fire and killed 12 students and a teacher.
It also resonated in the U.S. presidential race. Both President Barack Obama and his Republican rival, Mitt Romney, toned down their campaigns, pulled their ads from Colorado and dedicated their scheduled events to the victims.
Obama, who received a briefing on the shooting, pledged federal support for the investigation in a phone call with Aurora Police Chief Dan Oates, aides said.
"My daughters go to the movies," Obama told supporters at a campaign event in Fort Myers, Florida. "What if Malia and Sasha had been at the theater as so many kids do each day?"
The gunman was armed with an AR-15 assault rifle, a 12 gauge shotgun and a Glock .40 caliber handgun, Oates said. Police found an additional Glock .40 caliber handgun in his car, parked just outside the theater's rear emergency exit, Oates said.
Holmes, who had only a speeding ticket on his police record, was dressed in black with a gas mask, ballistic helmet, vest, throat guard and crotch guard, Oates said.
Oates said Holmes had purchased the weapons legally at three area gun stores in the last 60 days and had bought 6,000 rounds of ammunition.
The suspect bought a ticket, entered the theater and propped open the emergency exit while he slipped out to "gear up" and return armed, the law enforcement official said.
Holmes, a University of Colorado medical student, was in the process of dropping out of a graduate program in neurosciences, the university said in a statement.
Smart and carrying himself with a swagger, he treated children kindly but had trouble finding work, people who knew him said.
Billy Kromka, who served as a research assistant alongside Holmes for a couple of months last year, said he was stunned when he saw the news.
"He basically was socially awkward but not to the degree that would warrant suspicion of mass murder or any atrocity of this magnitude," Kromka said. "I did not see any behavior he exhibited that indicated he would be capable of an atrocity of a magnitude like this."
But New York Police Commissioner Ray Kelly said he "clearly looks like a deranged individual."
"He had his hair painted red, he said he was The Joker, obviously the enemy of Batman," Kelly told reporters, referring to a character in the Batman comic and cinematic universe known for committing acts of random, chaotic violence.
Holmes' family issued a statement of sympathy for the victims, saying, "Our heart goes out" to their loved ones, while they also asked for privacy from the media while they "process this information."
Hours after the shooting, authorities began removing bodies of victims from the theater while the investigation continued with some 200 local police, 100 FBI investigators and 25 representatives of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives on scene, officials said.
In New York, police pledged to deploy officers at all 40 theaters where "The Dark Knight Rises" was playing in part as a precaution against "copycats." Los Angeles police said they would increase patrols at screenings of the film.
The Paris movie premiere was canceled on Friday, event organizers said. Director Christopher Nolan called the shooting an "unbearably savage" event for which he expressed "profound sorrow" to the victims and their families.
Time Warner-owned Warner Bros., the studio behind the film, faced the prospect of seeing the blockbuster sink at the box offices even as the film got off to a strong start across the United States and Canada.
The film, with a budget of $250 million, opened on 4,404 screens, the second-widest release ever behind "Twilight: Eclipse," and industry analysts had said it stood a good chance of matching or beating the opening weekend box office record of $207 million set by Disney's "Avengers" in May.
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