(CNN) -- It was a dark theater, playing a movie that includes gunshots, in the middle of the night. So when a gunman burst through an exit door, threw a gas can into the crowd and began shooting, many inside the Aurora, Colorado, theater didn't realize what was happening.
Emma Goos saw a man come through the exit door at the front of the theater, wearing a gas mask and body armor and wielding a gun.
"I thought it was a joke at first," she said.
Jennifer Seeger, who was in Theater 9 at the Century Aurora 16 multiplex, said the shooter lit a gas can and threw it into the crowd, then he shot the ceiling to scare everyone.
"They just started scattering, and mass chaos just happened," she told CNN affiliate KCNC-TV in Denver.
"I was terrified, so I just dove into the aisle. And at that point he started shooting people behind me." Burning bullet fragments ended up on her forehead, she said. "I just told myself: 'I need to get out of here. I need to get out of here.'"
Police Chief Dan Oates said officers were on scene within 90 seconds of the first call and immediately detained suspect James Holmes near his car behind the theater. "The response was very rapid," he said.
The man suspected in the mass shooting had colored his hair red and told police he was "the Joker," according to a federal law enforcement source with detailed knowledge of the investigation.
Adam Witt told CNN that he and his wife had been looking forward to seeing the movie for months.
"The first thing I noticed was a hissing sound coming from the left side of the theater. I noticed people beginning to react in the area. I knew something was wrong," he said in an iReport.
"Then the gunshots began. A sudden flash of light and loud bang from the right side of the screen. Then another, and another. There must have been 20-30 at the least. At first glance they looked like fireworks or something, perhaps a prank."
But he soon realized what was happening.
"I hit the floor and hid behind the seats in front of me, pulling my wife down to hide with me. It was the longest minute of my life," Witt said. "The gunshots just kept coming. I knew it could be over any second. I knew my wife could be gone any second. It was absolutely surreal. I felt something hit my left arm, and my first thought was 'at least it's just my arm.'"
When the gunfire subsided people took to the exits en masse, he said. "I took my wife by the hand and we booked it for the back door, trying to breathe through the gas that now permeated the room."
The area was filled with people screaming -- in some cases, for their children, he said.
"The entire ordeal was completely surreal, and entirely horrifying."
An emotional movie patron told CNN that a man sitting next to him was shot. Two people he believes were the victim's teenage daughters tried to wake the man, according to Chris Ramos.
Ramos later saw the girls outside, on the phone.
"They were crying," he said. "Their dad was in there," in the theater.
Darius Harvey said the room was so dark it was difficult to see what was happening. "I couldn't see anything" -- not even the fumes he was breathing in, he said.
Trey Freeman, another witness, said the shooter threw a second gas canister. "He looked so calm when he did it, it was so scary," Freeman said in a YouTube video.
Moviegoer Quentin Caldwell, who was in an adjacent theater, said, "I think we were 15 minutes in, and there was a chase scene where there was gunfire on screen.
"And right then out of nowhere on the right side of us we hear a very distinct 'pop, pop, pop, pop.'"
Caldwell saw wounded people, including one young couple who was holding a bleeding woman by her face and guiding her down the stairs, Caldwell said.
"I looked to my right and another gentleman is holding his stomach and running down the stairs trying to get out of there," he said.
Even after he left the theater, some people stayed behind not understanding what happened and thinking the movie might continue, Caldwell said. "I looked at them like, 'This is real. There's something wrong. We need to leave now.'"
Witnesses described the man as dressed in black and wearing a gas mask and bulletproof vest.
When the gunman began shooting, "I thought there was no way I was going to get out of there without getting shot," Freeman said.
In the rush to leave, some people were stepped on or pushed, Derek Poag told CNN.
Outside the theater, it was chaotic, with wounded people everywhere, Caldwell said. He saw one girl in a pink hoodie, her left side peppered with wounds.
Cell phone video taken outside the doors of the theater complex showed panicked moviegoers calling out for help or searching for friends.
One man can be seen walking out with assistance, the back of his shirt covered in blood. A woman examines her body, as if checking for wounds.
Donovan Tate said he saw a man crawling, a girl spitting up blood, and people with bullet holes in their backs. "There was this one guy who was stripped down to his boxers, it looked like he had been shot," perhaps in the back, Tate said. "It was crazy."
Alex Milano was in the next theater over that was also showing the Batman film.
He also said there was a shooting scene happening on screen when the sound of real bullets was heard nearby.
"Loud bangs came from the right of the theater. Smoke took over the entire theater, and it was really thick and no one could really see anything," he said.
Confused at first, Milano realized the severity of the incident when he saw "objects" starting to come through the wall, presumably bullets.
"I saw holes in the wall," he said.
Some people in his theater started moaning in pain, and alarms at the building started sounding.
Outside, Milano spoke with a woman who was inside Theater 9. What she heard "sounded like madness to me," he said.
One scene stuck in his head -- a police officer carrying a little girl in his arms. The girl wasn't moving.