(CNN) -- Jennifer Seeger stared at the gun pointed at her face in a darkened movie theater.
The 22-year-old had two choices: Stand there and die, or make a run for it.
She made a split-second decision and dived into a row at the Century Aurora 16 multiplex, tucking herself under the seats.
The gunman shot into the row, and then into the row behind Seeger. Bullet casings, burning hot, dropped around her.
Play dead, she told people as the shooting continued. He won't shoot people he thinks are already dead.
In the movies, violence is coordinated. Explosions are perfectly timed. Gunshots ring out clearly. Bodies fall slowly.
But when violence strikes in real life, it is chaotic and often muffled.
That's the scene that unfolded early Friday morning, shortly after midnight, when a gunman opened fire at a movie theater in Aurora, Colorado, during a screening of the new Batman sequel.
In the few minutes it took the gunman to unload hundreds of rounds, according to police estimates, nearly everyone inside Theater No. 9 would make a life-or-death decision -- sometimes with terrifying results.
The theaters of the Century 16 multiplex were filled with hard-core fans, many of whom bought tickets weeks earlier for the 12:05 a.m. premiere of "The Dark Knight Rises." Many wore costumes that emulated their favorite characters in the DC Comics franchise.
In the front of the theater, Seeger and a friend took seats in the second row, close to the screen. Emma Goose, 19, and her friends arrived late and were forced to take separate seats close to the front, also near the screen.
The gunman was there, too. He bought a ticket at the door and took a seat near the emergency exit door, according to police.
'Oh my God'
The movie was in its first minutes and most of the moviegoers didn't appear to notice the exit door open and then only partially close.
Authorities believe it was then that the gunman sneaked out to his car parked in the rear of the theater to pick up weapons and don a gas mask and tactical gear, including a ballistic helmet and protective gear for his legs, throat and groin.
It was shortly after 12:35 a.m. when Seeger first saw the man wearing a gas mask and toting weapons enter the theater through the emergency exit door.
He looked like "a SWAT man," decked out head-to-toe in black, Seeger thought.
It must be part of the show, she reasoned, an added attraction on the opening night of one of the most highly anticipated movies of the year.
Goose thought the same thing.
In one hand, the man held a hissing canister, they said. In the other, a rifle.
Seeger watched him as he lobbed the canister into the audience. It made a loud popping sound, witnesses say.
He then pointed the rifle toward the ceiling, firing several rounds.
In that moment, Seeger knew it was not an act. So, too, did Goose.
"Oh my God, this is really happening," Goose thought, as she went to the floor.
Then the man lowered what is now believed to be a semi-automatic rifle, pointing it at Seeger as she stood up.
'Crawling over each other'
Panic was setting in as a realization swept through the theater that the gunman was real -- and he was planning on killing people.
Whatever was in the canister that landed in the middle of the theater was beginning to burn the eyes of the patrons.
Some in the theater thought it was a smoke bomb, while others believed it was tear gas.
At first, Seeger didn't know what to do. The gunman was three feet away, pointing a gun at her face.
There wasn't time to make a reasoned decision. You either live or die, she told herself.
Seeger dived into the row, pushing her body underneath the seats next to her friend as she heard gunshots around her.
She quietly tried to calm her friend and those around her as hot shell casings bounced on the floor and hit her in the face, burning her forehead.
In a nearby row, Goose was on the floor, using the seats for cover, when she realized she had to move if she was going to survive.
"We started pushing each other and crawling over each other," she said.
The first 911 calls came into the Aurora Police Department at about 12:39 a.m. They were followed by dozens, perhaps hundreds more.
The voice of a dispatcher crackled over the radio to police units: "They're saying someone is shooting in the auditorium." Moments later, she added: "There is at least one person shot, but they're saying there's hundreds of people just running around."
'Shot in the face'
People were pushing and shoving one another to try to get out of the tight rows of seats and down the aisles to safety.
Goose peered over the row of seats toward the gunman, who was now making his way toward the steps in the stadium-seating theater.
The gunman, witnesses would say later, walked slowly as he randomly fired at people. He shot at those who stood up and tried to flee, some said. He shot at people as they sat in their seat, said others.
She pulled out her phone to call 911 but then hid it after it lit up, fearing the gunman might see it and open fire in her direction.
Goose saw people, including a friend, run toward the hallway that served as one of the main entrances and exits for the theater. Some were wounded.
It was 12:40 a.m. when police first arrived at the theater, with one officer radioing: "I've got people running out of the theater who were shot."
Another said: "Got a victim who was shot in the face."
Then the dispatcher orders "all available units to respond to the theater."
Seeger pulled herself out from under the seats and peered over the seats to see the gunman walking up the steps toward the back of theater.
For a moment, the shooting stops. Seeger said it appeared he ran out of ammunition and was either reloading or getting another gun.
It was then she told people around her to "make a run for it."
But as the people began crawling and, in some cases, running toward the exit, the gunman turned and began firing on them.
"Lay down, be very still. Play dead," she told people as the crawled back toward her. "He won't shoot people he already thinks are dead."
Outside, by 12:42 a.m., police officers were surrounding the multiplex and other officers were making their way toward the theater where one smelled what he described over the radio as pepper spray.
"Get us some damn gas masks for Theater 9, we can't get in," one of the officers said.
Inside the theater, Seeger lay on the floor and played dead.
In a nearby row, Goose was trying to figure out how to get out. People were still trying to flee, and the gunman was still shooting.
In the dark, with the gunman moving toward the back of the theater, Goose crawled across the aisle -- to another row of seats near the exit. It was the same place a friend of hers was forced to sit when they couldn't find seats together.
But as soon as she cleared the aisle, she stumbled onto a man in the row who had been shot in the head. "He was grazed but bleeding a lot," she said.
Bodies in aisles
As suddenly as the shooting started, it stopped. The gunman was gone.
People, some soaked in blood, began running for the main exit.
Goose helped the wounded man out of the theater, while Seeger picked herself up off the floor and surveyed the carnage. There were bodies in the aisle, and people slumped over in seats who at first glance appeared to be dead.
Nearby, she thought heard a man "mumbling." She checked his pulse, her training as an emergency medical technician kicking in.
He was alive, but barely.
Her friend begged her, even screamed at her to leave the theater. But Seeger couldn't. Not yet.
Seeger grabbed the man under his arms and tried to drag him out of the row of seats, toward the exit.
Suddenly, there was screaming. Moviegoers were saying the gunman had returned.
Seeger was forced to flee, forced to leave the man behind.
The gunman, though, was gone.
Goose, Seeger and others aren't sure how the shooter got out of the theater, whether he went through the emergency exit or some other door.
Outside, in the rear parking lot of the theater, officers radio at 12:46 a.m. that they had spotted a man who matched the description given by people who had fled the theater.
"We've got rifles, gas mask. He is detained," one officer radioed. "I've got an open door going into the theater."
The gunman identified himself to arresting officers as "the Joker," a law enforcement official later said.
From inside the theater, at about the same time, another radio dispatch: "I need someone to shut this movie off. Have them shut the movie off in 9."
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CNN's Tom Foreman, Phil Gast, Don Lemon, Ed Lavandera, Susan Candiotti and Mariano Castillo contributed to this report.