A former neuroscience honours student – clad in SWAT gear, body armour and a mask – opened an emergency door to a packed movie theatre, tossed in two cans of gas and opened fire, killing at least 12 and wounding at least 59 attendees watching the midnight premiere of The Dark Knight Rises near Denver, Colo.
Police identified the suspected gunman as 24-year-old James Eagan Holmes, a graduate student at the University of Colorado who was in the process of withdrawing from his academic program.
The suspect had also booby-trapped his apartment in the city of Aurora with explosive devices, leading the police to evacuate five buildings in the neighbourhood as they sought to disable "incendiary and chemical devices" that appeared to be rigged to trip wires.
The incident has plunged the United States into a soul-searching exercise over the gun crime that plagues its communities, across all divides and venues.
"I'm sure many of you are parents who had the same reaction I did when we heard the news," President Barack Obama said Friday in response to the killings. "My daughters go to the movies. What if Malia and Sasha had been at the theatre as so many kids do each day?"
In the corner of a parking lot next to the Christian Fellowship Church, looking out across police lines to the Century 16 movie theatre where the slaughter happened, a small group of people stood in silence Friday night.
Cara, a young woman who would not give her last name, bounced her three-year-old daughter in her arms and cried quietly to herself.
"I lost three family friends over there last night," she said. "Three enlisted gentlemen from the air base. I'm angry. I'm sad. I don't know what to think."
Three separate screenings of the final instalment in the Batman trilogy got under way shortly after midnight at the Century 16 multiplex in Aurora, around 16 kilometres east of Denver. The suspect entered the theatre in riot gear, brandishing a handgun and a rifle. He set off gas canisters and started firing.
"I thought it was showmanship. I didn't think it was real," said Jennifer Seeger, who sat in the second row, 1 1/2metres from the gunman.
Patricia Legarreta, 25, said she was hit in the leg as she escaped with her four-year-old daughter, Azariah, and four-month-old, Ethan."He [the killer] was heading toward my daughter. Had I not moved I don't know what would have happened to her."
Her partner, Jamie Rohrs, 25, jumped six metres from a balcony with Ethan in his arms. He said: "I thought he was going to shoot the baby so I just jumped over the side.There were gunshots flashing to my right and people were falling, it was like a dream."
"Get us some damn gas masks for theatre 9. We can't get in it," one police officer told the dispatcher.
Bullet injuries were reported in adjacent theatre 8. The victims, who were being treated in six hospitals, included a six-year-old child. A four-month-old baby was treated and released. The oldest reported patient was 45.
Police detained the suspect in the parking lot of the multiplex without resistance. He is to be arraigned at 8:30 a.m. on Monday at Arapahoe County court in Littleton, Colo.
New York city Police Commissioner Raymond Kelly – who used to work with Aurora's police Chief Dan Oates – said the suspect had painted his hair red and called himself the Joker, the villain from the Batman movies.
The suspect's only previous encounter with Aurora police was over a traffic ticket. A university official said Mr. Holmes was one of the quieter people in the lab, spending much of his time on the computer, immersed in role-playing online games.
Retiree Karla Taylor was outside of the theatre paying respects to the victims. Asked if she linked the movie and the shooting, she shook her head.
"I think it's just a nut and I think it is a people thing, not a gun thing," she said. "Look at Columbine. They were blaming that on video games … but there was something about those kids that was just not right."
Friday's shooting took place 30 kilometres from Littleton, Colo., the scene of the Columbine High School massacre on April 20, 1999, in which two students killed 12 classmates and a teacher.
"Why do all these bad things happen here?" asked Taylor, a twentysomething student standing outside the theatre.