All of the guns used in the Aurora, Colo., movie theater shooting were legally purchased in the past six months, a law enforcement source told CNN.
The shooter was carrying a drum magazine, which is capable of holding more than 100 rounds of ammunition, the source said.
The shooting happened at an Aurora, Colo., movie theater screening the new Batman film early Friday. Twelve people were killed and 59 were wounded, officials said. The suspect, James E. Holmes, also left his apartment rigged with traps, police said.
"It's booby trapped with various incendiary and chemical devices and trip wires," Aurora Police Chief Dan Oates said, adding that it could take days to work through the apartment safely.
Five buildings around suspect Holmes' Aurora apartment were evacuated, Oates said.
Police said Holmes, 24, dressed head-to-toe in protective tactical gear, set off two devices of some kind before spraying the theater with bullets from an AR-15 rifle, a 12-gauge shotgun and at least one of two .40-caliber handguns police recovered at the scene.
Oates said investigators are "confident" that Holmes acted alone.
The shooting unfolded inside a darkened theater packed with Batman fans, some in costume for the premiere of the movie "The Dark Knight Rises." Screaming, panicked moviegoers scrambled to escape from the black-clad gunman, who wore a gas mask and randomly shot as he walked up the theater's steps, witnesses said.