At first, he appeared as a silhouette.
Some people in the crowded theater thought he was a stunt that was part of a late-night showing of The Dark Knight Rises, one of the summer's most highly anticipated films.
But then the gunman, wearing a helmet, body armor and a gas mask, threw gas canisters that filled the packed suburban Denver theater with smoke.
In the confusing haze between Hollywood fantasy and terrifying reality, he opened fire as people screamed and dove for cover.
At least 12 people were killed and 59 wounded in one of the deadliest mass shootings in recent U.S. history. Some were shot; other died of other injuries, Aurora police Chief Dan Oates said Friday night.
"He looked like an assassin ready to go to war," said Jordan Crofter, a moviegoer who was unhurt in the attack early Friday.
The suspect, identified by police as 24-year-old James Holmes, used a military-style semi-automatic rifle, a shotgun and a pistol, stopping only to reload.
The suspect marched up the aisle in the stadium-style theater, picking off those who tried to flee, witnesses said. Authorities said he hit scores of people. One of them was struck in an adjacent theater by gunfire that went through the wall.
"He would reload and shoot and anyone who would try to leave would just get killed," said Jennifer Seeger, adding that bullet casings landed on her head and burned her forehead.
Within minutes, frantic 911 calls brought some 200 police officers, ambulances and emergency crews to the theater. Holmes was captured in the parking lot. Police said they later found that his nearby apartment was booby-trapped.
Authorities gave no motive for the attack. The FBI said there was no indication of ties to any terrorist groups.
In New York City, police Commissioner Raymond Kelly said: "It clearly looks like a deranged individual. He has his hair painted red. He said he was the Joker, obviously the enemy of Batman."
Oates would not confirm that information, but did say he had spoken to Kelly. The two used to work together in New York. Asked whether Holmes had makeup to look like the Joker, Oates said: "That to my knowledge is not true."
It was the worst mass shooting in the U.S. since the Nov. 5, 2009, attack at Fort Hood, Texas. An Army psychiatrist was charged with killing 13 soldiers and civilians and wounding more than two dozen others.
It was the deadliest in Colorado since the Columbine High School massacre in suburban Denver in 1999, when two students killed 12 classmates and a teacher and wounded 26 others before killing themselves.
The new Batman movie, the last in the trilogy starring Christian Bale, opened worldwide Friday with midnight showings in the U.S. The plot has the villain Bane facing Bale's Caped Crusader with a nuclear weapon that could destroy all of fictional Gotham.
The shooting prompted officials to cancel the red-carpet premiere in Paris, and some U.S. movie theaters stepped up security for daytime showings.
The film's director, Christopher Nolan, issued a statement on behalf of the cast and crew, expressing their "profound sorrow at the senseless tragedy."
"Nothing any of us can say could ever adequately express our feelings for the innocent victims of this appalling crime, but our thoughts are with them and their families," Nolan said.
The attack began shortly after midnight at the multiplex in Aurora, an urban community on Denver's east side. Audience members said they thought it was part of the movie, or some kind of stunt associated with it.
The film has several scenes of public mayhem, a hallmark of superhero movies. In one scene, Bane leads an attack on a stock exchange, and in another he leads a shooting and bombing rampage on a packed football stadium.
A federal law enforcement official said Holmes bought a ticket to the show, went into the theater as part of the crowd and propped open an exit door as the movie was playing. The gunman then donned protective ballistic gear and opened fire. The official spoke to the Associated Press on condition of anonymity, citing the ongoing investigation.
At some point the gunman must have stepped outside, because several witnesses saw him come through the door.
"All I saw is the door swinging open and the street lights behind, and you could see a silhouette," said Crofter, who was sitting on the left side of the theater and toward the front.
Sylvana Guillen said the gunman, clad in dark clothing, appeared at the front of the theater as the character Catwoman appeared in the movie. Then they heard gunshots and smelled smoke from a canister he was carrying.
As she and her friend, Misha Mostashiry, ran to the exit, Guillen said, they saw a man slip in the blood of a wounded woman he was trying to help.
Oates said the gunman wore a gas mask and a ballistic helmet and vest, as well as leg, groin and throat protectors. He said among the guns was an AR-15 rifle and that the gunman used two gas canisters.
Later, police began entering the theater, asking people to hold their hands up as they evacuated the building.
Some of the victims were treated for chemical exposure apparently related to canisters thrown by the gunman. Those hurt included a 4-month-old baby, who was treated at a hospital and released.
Authorities started to remove the bodies from the theater on Friday afternoon. Ten people died in the theater, while two others died from their injuries later.
Politics pushed aside
President Barack Obama tells a Florida audience that this is not the day for politics, canceling rallies and heading back to Washington. Story, 3A