AURORA, Colo. -- A gunman wearing a gas mask opened fire early Friday at a suburban Denver theater at the opening of the Batman movie The Dark Knight Rises, killing 12 people and injuring 38.
The gunman, who is in custody, stood at the front of the theater and fired into the crowd at around 12:30 a.m. MT at a multiplex theater in a mall in Aurora, police said.
Federal law enforcement officials, who declined to be named because they are not authorized to discuss the case, identified the suspect as James Holmes, 24, of Aurora.
Aurora police said the suspect offered no resistance when he was arrested at the rear of the theater. Police said he had a rifle, handgun and gas mask when he was arrested. Another gun was found in his car.
"Witnesses tell us he released some sort of canister. They heard a hissing sound, and some gas emerged, and the gunman opened fire," Aurora Police Chief Dan Oates said at a news conference.
Oates said 10 victims died at the theater and two died at area hospitals.
FBI spokesman Jason Pack said there's no indication in the investigation of any connection to terrorism. At least 100 federal agents are involved in the investigation.
Authorities have reported no evidence of any other attackers. There was no immediate word of any motive.
Police, ambulances and emergency crews swarmed to the scene after frantic calls flooded the 911 switchboard.
A police officer could be heard over a police scanner yelling, "Get us some damn gas masks for Theater 9, we can't get in."
Officers came running in and told people to leave the theater, Salina Jordan told The Denver Post. She said some police were carrying and dragging bodies.
Moviegoers were confused at first because there was an on-screen gunbattle happening at the time the shooting started.
"We all thought it was a joke," said Joseph Soto, 18, who was in an adjacent theater when shots rang out. "We found out it wasn't a joke."
Rounds from Theater 9 where the shooting occurred came through the wall into Theater 8 where he was sitting, Soto said. He said theater staff ushered patrons out a side door, warning them not to go out the main entrance.
"It was relatively calm for what was happening," he said.
Oates said the suspect spoke of possible explosives in his residence. "We are dealing with that potential threat," he said.
Police were at the Denver-area apartment where the suspects lives and had evacuated other residents of the building.
Oates said police also checked for explosives in the parking lot and at the Century 16 theater and secured those areas.
President Obama said he was saddened by the "horrific and tragic shooting," pledging that his administration was "committed to bringing whoever was responsible to justice, ensuring the safety of our people and caring for those who have been wounded."
Obama canceled campaign stops in Florida and headed back to Washington.
Department of Homeland Security Secretary Janet Napolitano said, "We are committed to bringing those responsible to justice. Our hearts and prayers go out to anyone impacted by this tragedy, especially the family and friends of those killed or injured."
Moviegoers spoke of their terror when the violence erupted and people around them fell victim.
Benjamin Fernandez, 30, told the Post he heard a series of explosions. He said people ran from the theater and there were gunshots as police shouted, "Get down!"
Fernandez said he saw people falling, including one young girl.
Jordan told the paper one girl was struck in the cheek, others in the stomach, including a girl who looked to be around 9 years old.
Jordan said it sounded like firecrackers until someone ran into Theater 8 yelling, "They're shooting out here!"
Hayden Miller told KUSA-TV that he heard several shots.
"Like little explosions going on and shortly after that, we heard people screaming," he told the station.
Hayden said at first he thought it was part of a louder movie next door. Then he saw "people hunched over, leaving the theater."
Some people in the audience thought the thick smoke and gunfire was a special effect accompanying the movie, police and witnesses said.
"We just heard a pop, pop, pop, pop," Quentin Caldwell, who was attending the Batman showing in an adjacent theater, told CNN.
Victims were transported to at least six area hospitals. Many were rushed immediately to hospitals in police cars by responding officers.
KUSA reported that some hospitalized victims were being treated for chemical exposure, possibly related to a canister thrown by the gunman.
Eleven people were treated at the Medical Center of Aurora for gunshots, and injuries ranged from minor to critical condition. Two others walked in to be treated for tear gas contamination.
Denver Health had seven victims -- one in critical and the rest in fair condition.
The youngest victim, a 3-month-old infant, was treated and released from the hospital, according to KUSA. Six victims were treated at the Children's Hospital. Their condition wasn't known.
Two people in critical condition were rushed to nearby Swedish Medical Center, spokeswoman Nicole Williams said.
At the Gateway High School, which officials used as a staging area, witnesses were provided mental health counseling through the Red Cross while they waited to talk to investigators.
Father Michael Borgstede of the nearby Mount Olive Lutheran Church said victims and witnesses need a "listening ear."
Borgstede said he walked over to the school to provide whatever counsel he could. "I'm just hoping to sit with them and pray," he said.
Eric Soto, 42, was at the school with his son Joseph. "He called me about 12:30 and said, 'Come pick me up, Dad, come pick me up.' I could tell he was nervous," Soto said.
"He said it sounded like firecrackers," Soto said, standing outside the school while his son was interviewed by investigators.
Aurora is on Denver's east side and is Colorado's third-largest city with 327,000 residents. It is home to a large Defense Department satellite intelligence operation at Buckley Air Force Base, as well as the Children's Hospital, the University of Colorado Hospital and a future Veterans Affairs hospital.
Officials in the area scrambled to use social media to get word out about the shooting.
"We certainly appreciate the nation's thoughts and prayers as our police department continues to investigate the terrible theater shooting tragedy that occurred today," said a statement posted on the city's Facebook. "Our condolences go out to the victims and their family members."
The Red Cross used Twitter to urge people who were in the theater to use social media to alert friends and family that they are safe. Spokesman Patricia Billinger recommended that area residents update their Facebook and other social media accounts to let their friends know they are safe.
Billinger said that during all the uncertainty about who was at what showing of the popular movie, taking that extra step will help reassure family and friends.
"People don't know how close you were, so help alleviate that anxiety," she said.
Warner Bros. Entertainment released a statement that said, "Warner Bros. is deeply saddened to learn about this shocking incident. We extend our sincere sympathies to the families and loved ones of the victims at this tragic time."
The company canceled the Paris premiere of the movie, saying it would be inappropriate in light of the tragedy.
New York City Police Commissioner Ray Kelly said the department plans to provide extra security at theaters in the five boroughs showing the new movie.
By Trevor Hughes and Carolyn Pesce