Last Updated 10:42 a.m. ET
(CBS/AP) Eyewitnesses described scenes of panic, chaos and patrons covered in blood after a gunman opened fire with assault weapons at an Aurora, Colo., multiplex shortly after midnight Friday.
At least 12 people have died; Dozens more were wounded.
The violence occurred at midnight screenings of the opening of the new Batman film, "The Dark Knight Rises."
"I went out to enjoy a movie and I ended up in a gruesome thing - I don't know how you would qualify it," witness William Kent told CBS News.
Police said the suspect appeared at the front of the crowd in Theater 9, threw some type of gas or explosive device, and started shooting.
A woman named Jennifer Seeger told CBS Station KCNC that the gunman came in, lit a gas canister and threw it into the crowd. "At that point he shot his first fire into the ceiling to scare everybody. They started scattering - mass chaos just happened."
"He pointed the gun at me," she said. "I was terrified, so I just dove into the aisle. At that point he started shooting people behind me. I had bullets that were on my forehead, burning my forehead, and I told myself, I need to get out of here.
"I crawled on the ground and I just laid in a ball and waited for him to go up the stairs," Seeger said, then told her friend that they had to leave. "At that point, I was trying to crawl out but then everybody was crawling back in and saying, 'Don't go over there. He's going to shoot everybody trying to get out of the main doors,' and he was. All I hear is gunshot after gunshot. Just women and children are screaming."
She said the gunman was wearing a gas mask and so she could not see his face.
"I don't know exactly what kind of gun it was, it was just a big rifle . . . They were big bullets, too, and they were hot. I smelt gunfire in the air. I was just terrified. The gas was getting to me. I was having a hard time breathing."
The assailant was seized at the scene. A law enforcement source told CBS News the suspect was well-equipped, with one rifle, two handguns, a knife, bulletproof vest, ballistic helmet, gas device, gas mask and military/SWAT-style clothing. There were also unidentified explosives found in his vehicle.
CBS News senior correspondent John Miller said on "CBS This Morning" that Seeger is lucky to be alive. He said, "She said she felt bullets burning her forehead. What she's talking about is stippling, which is the gun was being fired so close in front of her that the gunpowder and burn that comes out of the barrel and where it's ejected actually was hitting her skin as the bullets went by. So the witness we just heard - that vivid description - is extraordinarily lucky, as I think she understands, to not be one of the gunshot victims and to be around talking."
Corbin Dates told CBS News correspondent Barry Petersen he saw a man take a phone call by the emergency exit and possibly try to signal or look for somebody during the movie's opening credits. After the movie started, the emergency exit door swung open.
"Somebody walks in dressed all in black, helmet, gas mask, black outfit, you cannot see anything but the person's eyes," said Dates, "and there was a gas can that was thrown into the audience behind me. It went off. I thought it was a stunt of the movie, so I didn't think anything serious of it once it went off."
When gunshots went off, Dates and his friend dropped to the floor and started to crawl through the theater, he said.
"I felt the caps from the bullets burn my leg," Dates said.
Another woman, Spenser Sherman, told "CBS This Morning" that she saw the emergency exit door open and a tear gas thrown in. "Then it was a blur," she said. "Then I heard a couple gunshots."
"I thought it was part of the movie, like a fun little prank - that it would be over in a few seconds. It obviously wasn't."
She said she only saw a silhouette of the suspect, and that the gunman said nothing.
"Everybody had dropped to the floor after the first couple gunshots, and then he fired some more. And then after that, there was a pause in the gunshots. Some people say he was reloading, I don't know. But at that point, my boyfriend was like 'This is the time, we need to go, we need to get out of the theater right now.' So we ran."
She and her friends got out safe. Sherman said she saw one woman with blood on her face. "It's really mind-boggling that someone would turn an event like this into something this terrible."}
"As I walk out, I see that young girl shot, blood, everything that I would never expect to see in real life," Shayla Roeder, who left the multiplex, told CBS News. And I just keep looking around seeing what's my surroundings, and I see people walking out with blood on them. I'm still thinking maybe this is just, you know, maybe nothing is really going on here. And I'm walking out seeing everyone else walking out nonchalantly with blood on them. Police officers following them saying we need ambulances out.
"And then what really caught me off-guard is, there was a girl, like 24 or 25-years-old, my age. She said, 'I just need someone to talk to. One of my best friends just got shot and I don't know who to talk to right now.'"
Witnesses report bullets passed through the wall into Theater 8, where Kent was watching the movie. Initially, Petersen reports, audiences in Theater 8 did not know that the sounds of gunfire were not part of the film.
"There was a lot going on in the soundtrack of the movie at that time. In the beginning, I don't think people realized what was happening," said Kent, who saw evidence of bullets passing through the walls.
"They started the fire alarm, or the emergency alarm - said that there had been something that happened in the building and they evacuated everybody. There was a huge commotion to get out of the theater," said Kent. "When I exited, there were police officers with assault rifles running in."
Salina Jordan told the Denver Post she saw police carrying and dragging bodies.
Donovan Tate told KCNC that he saw a girl spitting up blood. "There were bullet holes in some people's backs, in some people's arms. There was one guy who was just stripped down to his boxers. It looked like he had been shot in the back," Tate said.
It was the worst mass shooting in the United States since 32 people were killed on the Virginia Tech campus in 2007.