Police said Holmes set off two gas-emitting devices before spraying the theater with bullets from an AR-15 rifle, a 12-gauge shotgun and at least one of two .40-caliber handguns that police recovered.
"There was blood everywhere," Christina Blache, a shooting victim, told CNN's Don Lemon from her hospital bed Saturday. Her friend was one of those killed.
"You're sitting in a movie theater trying to watch a movie with your friends. Who expects to be shot in a movie theater? None of us did," she said.
Holmes had bought the guns legally at stores in the Denver area over the past two months, Oates said. More than 6,000 rounds of ammunition were also purchased online, according to the police chief.
A receipt obtained by CNN shows Holmes bought some of the tactical gear, including a vest and a magazine pouch, online on July 2.
Holmes surrendered without resistance within seven minutes of the first 911 calls from moviegoers, Oates said. He was arrested in the theater's rear parking lot.
"If you think we're angry, we sure as hell are angry about what has happened to our city, what has happened to these wonderful people who live here, and also what he threatened to do to one of our police officers," the police chief said.
The Joker has long been a fixture in Batman comics and was famously portrayed by Heath Ledger in 2008's "The Dark Knight," the predecessor to "The Dark Knight Rises." Ledger, who died in 2008, won a posthumous Academy Award for his portrayal of the villain who encourages anarchists to take over Gotham City.
Holmes, who is being held in Arapahoe County Jail, is scheduled to appear in court on Monday morning. The court file was sealed, according to a court order.
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