Throwing at least one tear-gas canister, the suspect unleashed birdshot into the first few rows of the audience watching “The Dark Knight Rises,” said the official, who asked for anonymity. He then switched to a rifle, targeting people throughout the theater. When the gun jammed, he used a pistol, the official said.

A suspect, James Holmes, 24, was arrested after the 12:30 a.m. attack at a shopping mall that housed the theater in the Denver suburb, Police Chief Dan Oates said at a press briefing. Oates said there is no information about the motive.

“Our hearts are broken,” Colorado Governor John Hickenlooper said at the news conference. “There isn’t one of us who has children who doesn’t think of this as being your child in this theater. It makes the pain of this grief too intense for words.”

Many of the wounded are in critical condition, Oates said. Two victims died at hospitals, and 10 bodies are still at the crime scene, he said.

The shooting was the worst in the U.S. since 13 soldiers and civilians were killed and 43 wounded when a gunman opened fire at Fort Hood, Texas, in 2009.

Fatal Errand

The gunman bought a ticket, entered the Century 16 Movie Theaters at the Aurora Town Center and watched the movie for a while, then stood as if taking a phone call and walked out, propping open the door as he left, the federal official said. The killer went to his vehicle, donned a helmet and ballistic vest, armed himself and returned.

After the rampage, Holmes was confronted by armed police, the official said. He surrendered, telling police he had explosives on him. The police stripped the suspect naked and found none, the official said. In later interrogation, Holmes told authorities his home was booby-trapped, according to the official.

There are several bottles of an unidentified liquid connected by wiring across the floor and “other potentially explosive devices,” Deputy Fire Marshal Chris Henderson said. Officers had the neighborhood around the brick, three-story building cordoned.

Arsenal Amassed

Police got the first call about the shooting at 12:39 a.m. and ultimately received hundreds, Oates said. He said 25 officers arrived within a minute and a half and apprehended Holmes behind the theater where his car was parked.

Authorities seized two .40 caliber pistols, a Glock G22 and a Glock G23, a Smith & Wesson M&P .223 caliber semiautomatic rifle and Remington 870 Express Tactical 12-gauge shotgun, the federal official said.

Investigators found that Holmes began buying the weapons in May at stores in the Aurora region, the official said. The suspect hadn’t committed offenses that would have raised alarms during background checks, the official said.

Employees at a store that sold two of the weapons notified authorities of the purchases during the investigation, and there’s no information any dealers did anything illegal, the official said.

Graduate Education

Holmes was a graduate student in neuroscience at the University of Colorado-Denver who enrolled in June 2011 and was in the process of withdrawing, according to a statement from the school.

He attended high school in San Diego County, California, where his parents and other relatives still live, according to the U-T San Diego newspaper.

“Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved,” the family said in a statement.

Holmes had one traffic summons for speeding in October 2011, Oates said. Arapahoe County District Attorney Carol Chambers said Holmes will be in court next week but declined to specify a date. He’s currently in county jail, Oates said.

“The Dark Knight Rises” is rated PG-13 and there were many children, including some in costumes, at the Century 16, owned by Cinemark Holdings Inc. (CNK)

The movie’s maker, Time Warner Inc. (TWX), canceled the Paris premiere after the shooting and issued a statement of sadness and sympathy for the victims. Warner Bros. is canceling sometelevision advertising for “The Dark Knight Rises,” according to two people with knowledge of the matter. In New York City, Police Commissioner Raymond W. Kelly deployed officers to theaters showing the movie.

‘Find My Son’

In Colorado, police brought unhurt witnesses to nearby Gateway High School. Tom Sullivan came holding a picture of his 27-year-old son, Alex. Sullivan said Alex was at the movie and has been missing since the shooting.

“Find my son,” he yelled from the parking lot at the high school, which is being used as shelter with grief counselors for people looking for friends and relatives.

Evelyn Marquez, 20, and her boyfriend, Fernando Santos, 20, said in an interview that the theater was packed.

“It took us a couple of seconds to really realize what was going on,” Santos said.

Crawling Away

The theater filled with acrid smoke and breathing became difficult, he said.

The man lifted what they thought was a stick. It was a gun. Santos and Marquez hit the ground and people began crawling over them, she said. Sparks flew off seats behind them, Santos said. He said he saw people struck by bullets.

They crawled to an exit.

Jennifer Seeger, 22, who is studying to be an emergency medical technician, said the man pointed his gun at her. She said she dove to the ground and sensed bullets flying by her face.

One teenage victim, she said, had a bullet in his back.

“I felt his pulse,” she said. “It was really weak. Everyone said ‘Run, run.’ I tried to pull him out, but he was too heavy.”

Emma Goos, 19, a student at St. John’s College in New Mexico, said she lost a shoe trying to escape the theater. She said people slipped on a floor greasy with popcorn butter.

Movie Night

One victim was identified as Jessica Ghawi by friends and her brother Jordan Ghawi in Twitter and blog posts. Ghawi was an aspiring sports journalist, they said.

“Never thought I’d have to coerce a guy into seeing the midnight showing of The Dark Knight Rises with me,” Ghawi, whose professional name was Jessica Redfield, posted on Twitter before the movie. She followed with: “Actually won the argument. he’s going! WIN!!!”

Some members of the U.S. military were among the victims, Pentagon spokesman George Little said today.

It wasn’t the Denver area’s first mass killing. In 1999, two students shot 12 classmates and a teacher in Columbine High School in suburban Denver before killing themselves. The deadliest shooting in the U.S. in recent years is the Virginia Tech campus rampage of 2007, in which Seung-Hui Cho took 33 lives, including his own.

President Barack Obama said in a statement that he and first lady Michelle Obama were “shocked and saddened.”

Half-Staff

“We may never understand what leads anybody to terrorize their fellow human beings like this,” Obama said later in Fort Myers, Florida. “Such violence, such evil is senseless. It’s beyond reason.”

Mitt Romney, his Republican opponent, said in a statement he was “praying for the families and loved ones of the victims.”

Obama ordered U.S. flags flown at half-staff at federal facilities, public buildings, military bases and U.S. offices overseas until sunset July 25.

Mayors Against Illegal Guns, a 600-member coalition that advocates tightening background checks of buyers, called for action from the presidential candidates and Congress.

“No matter where you stand on the Second Amendment, no matter where you stand on guns, we have a right to hear from both of them concretely, not just in generalities --specifically what are they going to do about guns?” New York Mayor Michael Bloomberg, a co-chairman, said today on his weekly radio show. The mayor is founder and majority owner of Bloomberg News parent Bloomberg LP.

Quiet on Control

The candidates, who suspended their campaigns, have said little about gun control.

“The president believes that we need to take common-sense measures that protect Second Amendment rights of Americans, while ensuring that those who should not have guns under existing law do not get them,” White House press secretary Jay Carney told reporters aboard Air Force One today.

In April, Romney said he didn’t want new gun laws.

“We need a president who will enforce current laws, not create new ones that only serve to burden lawful gun owners,”the presumptive Republican nominee said in an April 13 speech to the National Rifle Association convention in St. Louis.

Aurora Mayor Steve Hogan said the city of 325,000 will move on from the shootings.

“We’ve taken a blow today, but we will get back on our feet,” Hogan said at a press conference.

To contact the reporters on this story: Jeff Bliss in Washington at jbliss@bloomberg.net; Jennifer Oldham in Denver at joldham1@bloomberg.net; Mark Niquette in Columbus at mniquette@bloomberg.net