(CBS/AP) CENTENNIAL, Colo. - Colorado prosecutors filed 24 counts of murder charges Monday against James Eagan Holmes, the former neuroscience student accused of killing 12 people and injuring 58 others at an Aurora movie theater.

Prosecutors also filed 116 counts of attempted murder against Holmes, who Aurora police said booby trapped his apartment with the intent to kill any officers responding there the night of the theater attack.

Holmes, 24, was not expected to enter pleas on Monday. He ultimately could verbally enter a plea, or his attorneys could enter it for him.

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Unlike Holmes' first court appearance July 23, Monday's hearing was not televised. At the request of the defense, District Chief Judge William Sylvester barred video and still cameras from the hearing, saying expanded coverage could interfere with Holmes' right to a fair trial.

Last week, Sylvester allowed a live video feed that permitted the world its first glimpse of the shooting suspect. With an unruly mop of orange hair, Holmes appeared bleary-eyed and distracted. He did not speak.

Investigators said Holmes began stockpiling gear for his assault four months ago and bought his weapons in May and June, well before the shooting spree just after midnight during a showing of the Batman film "The Dark Knight Rises."

The four guns retrieved from the shooting were purchased legally at three Colorado gun stores between May 22 and July 6, CBS News correspondent Bob Orr reports. A federal law enforcement source told CBS News that Holmes spent $15,000 fortifying his arsenal online. Authorities found a shipping label from BulkAmmo.com in a dumpster near Holmes' apartment, the source said. EBay was the vendor Holmes used to purchase some body armor, the source said.

Holmes was arrested by police outside the theater. Analysts said that means it's likely there's only one main point of legal dispute between prosecutors and the defense.

"I don't think it's too hard to predict the path of this proceeding," said Craig Silverman, a former chief deputy district attorney in Denver. "This is not a whodunit. ... The only possible defense is insanity."