(CNN) -- Authorities in the Colorado movie theater massacre found an AR-15 rifle drum magazine Friday capable of carrying 100 rounds, and the police chief said thousands of rounds of ammunition for various weapons had been bought online in the weeks prior to the shooting.
Police took suspect James Holmes, 24, into custody Friday after they say he set off two devices and sprayed the theater with bullets from an AR-15, a 12-gauge shotgun and at least one of two .40-caliber handguns police have recovered. Investigators are confident that Holmes acted alone, police said.
Aurora, Colorado, Police Chief Dan Oates said Friday night that Holmes had purchased four guns at "local metro gun shops," and bought over 6,000 rounds of ammunition through online transactions.
Assessing what authorities have pieced together about the shooting and the weapons recovered, Oates told reporters, "As far as we know, it was a pretty rapid pace of fire in that theater."
