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.