(CBS/AP) AURORA, Colo. - A gunman clad in body armor and wearing a gas mask opened fire on moviegoers at a midnight showing of the latest Batman movie Friday, killing 12 and injuring dozens more in one of the deadliest mass shootings in recent U.S. history.

The violent and chaotic scene erupted at about 12:30 a.m. local time as the suspected gunman, identified as 24-year-old James Holmes, stood at the front of one of the Century 16 theaters at the Aurora Mall where "The Dark Knight Rises" was playing. Witnesses reported that the gunman entered the theater through an emergency exit door and authorities said he threw two gas canisters before opening fire.

"Then it was a blur," Spenser Sherman told "CBS This Morning" 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."

Aurora Police chief Dan Oates said a total of 71 people were shot, including the dead. Of the 59 people wounded, some were critically injured, though Oates couldn't give an exact figure.