In the age of widespread social media, no trace of Holmes could be found on Facebook, LinkedIn, MySpace, Twitter or anywhere on the Web. Either he never engaged or he scrubbed his trail.
A longtime neighbor in San Diego, where Holmes grew up, remembers only a "shy guy ... a loner" from a churchgoing family. In addition to playing soccer at Westview High School, he ran cross country.
The bookish demeanor concealed an unspooling life. Holmes struggled to find work after graduating with highest honors in spring 2010 with a neuroscience degree from the University of California, Riverside, said the neighbor, retired electrical engineer Tom Mai.
Holmes enrolled last year in a neuroscience Ph.D. program at the University of Colorado-Denver but was in the process of withdrawing, said school officials, who didn't provide a reason. The school later said in a statement that he left the program in June 2012.
As part of the advanced program in Denver, a James Holmes had been listed as making a presentation in May about Micro DNA Biomarkers in a class named "Biological Basis of Psychiatric and Neurological Disorders."
In academic achievement, "he was at the top of the top," recalled Riverside Chancellor Timothy P. White.
Holmes concentrated his study on "how we all behave," White added. "It's ironic and sad."
Authorities say Holmes arrived at the theater dressed in black, outfitted in a gas mask, ballistic helmet, vest and leggings, black tactical gloves and protectors on his throat and groin. He was armed with an assault-style rifle, a shotgun and Glock handgun.
Police said he started his attack by tossing gas canisters into the theater, where he had bought a ticket for the midnight showing of "The Dark Knight Rises," the new Batman movie.
A federal law enforcement official, speaking on condition of anonymity, said Holmes bought four guns from retailers in the last two months.
Holmes bought his first Glock pistol in Aurora, Colo., on May 22. Six days later, he picked up a Remington shotgun in Denver. About two weeks later, he bought a .223 caliber Smith & Wesson rifle in Thornton, Colo., and then a second Glock in Denver on July 6 13 days before the shooting, the official said.
Holmes is not talking to police and has asked for a lawyer, according to a law enforcement official briefed on the investigation. Police found jars of chemicals in Holmes' booby-trapped apartment with wires nearby, the law enforcement official said.
When he surrendered meekly in the theater parking lot, Holmes told authorities what he'd done at his residence in Aurora.
"Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved," Holmes' family said in a statement Friday.