Police said James Holmes began buying guns at Denver-area stores nearly two months before Friday's shooting. He also received at least 50 packages in four months at his home and the University of Colorado that authorities are investigating to see whether they contained materials for the potentially deadly booby traps that police found in his apartment.
At the same time, the quiet 24-year-old was in the final weeks of the first year of a rigorous Ph.D. neuroscience program, where he took a three-part final exam required for students to progress in the program and was scheduled to give a presentation on MicroRNA Biomarkers before abruptly leaving in June.
Holmes is being held without bond on suspicion of multiple counts of first-degree murder after a shooting rampage minutes into a premiere of "The Dark Knight Rises" in Aurora early Friday that left 12 people dead and 58 injured.
He is scheduled for an initial hearing Monday and has been assigned a public defender.
Amid the continuing investigation of Holmes and his background, Sunday was a day for healing and remembrance in Aurora, with President Barack Obama arriving to visit with families of the victims and a vigil planned later in the evening.
Congregations across Colorado prayed for the shooting victims and their relatives. Churches sent out social-media appeals for neighbors who wanted to join in remembrance. Elderly churchgoers at an aging Presbyterian church within walking distance near Holmes' apartment joined in prayer, though none had ever met him.
Holmes was being held in solitary confinement at a Denver-area county detention facility and was not cooperating to authorities, Aurora Police Chief Dan Oates said.
"He lawyered up. He's not talking to us," the chief said.
Authorities are working with FBI behavioral analysts and are looking into Holmes' relationships to figure out a motive, which could take months, Oates said.
The gunman's semiautomatic assault rifle jammed during the attack at the Aurora movie theater, forcing him to switch to another gun with less firepower, a federal law enforcement official told The Associated Press. That malfunction and weapons switch during the shooting rampage might have saved some lives.
Oates said a 100-round ammunition drum was found in the theater but said he did not know whether it jammed or emptied.
The owner of a gun range told the AP that Holmes applied to join the club last month but never became a member because of his behavior and a "bizarre" message on his voice mail.
He emailed an application to join the Lead Valley Range in Byers on June 25 in which he said he was not a user of illegal drugs or a convicted felon, said owner Glenn Rotkovich. When Rotkovich called to invite him to a mandatory orientation the following week, he said he heard a message on Holmes' voice mail that was "bizarre - guttural, freakish at best."
View Holmes' Lead Valley Range application
He left two other messages but eventually told his staff to watch out for Holmes at the July 1 orientation and not to accept him into the club, Rotkovich said.
Three days after the massacre, it still remained unclear whether Holmes' professors and other students at his 35-student Ph.D. program noticed anything unusual about his behavior. His reasons for quitting the program in June, just a year into the five- to seven-year program, also remained a mystery.
The university declined to release any details of his academic record, citing privacy concerns, and at least two dozen professors and other staff declined to speak with the AP. Some said they were instructed not to talk publicly about Holmes in a blanket email sent to university employees.
Jacque Montgomery, a spokeswoman for the University of Colorado medical school, said that police have told the school to not talk about Holmes.
The university also took down the website for its graduate neuroscience program on Saturday.
Dan Keeney, president of DPK Public Relations in Dallas, said asking for silence from university employees because of a police investigation was appropriate, but taking down the website was "indefensible" for a publicly funded university unless the school believed it contained inaccurate information relating to the suspect.
"It's an indefensible action," he said. "It's disappointing to hear that they would take that action because it suggests that it's not in the public's interest to have access to that information and I think it is in the public's interest."
The school took down the neuroscience department's site at the request of faculty and staff who had privacy concerns, Montgomery said
The University of Colorado also disclosed it was cooperating with police who were looking into whether Holmes used his position as a graduate student to order materials in the potentially deadly booby traps that police said they found in his apartment.
The apartment was booby trapped with jars of liquids, explosives and chemicals that could have killed "whoever entered it," Oates said, noting it would have likely been one of his officers. Investigators spent hours removing the explosive materials Saturday.
Among the dead was a 6-year-old girl and a man who died on his 27th birthday and a day before his wedding anniversary. Families grieved and waited at hospitals, with police reporting 11 people still in critical condition as of Saturday.
While authorities continued to refuse to discuss a possible motive for one of the deadliest mass shootings in recent U.S. history, details about Holmes' background as a student and would-be scientist trickled out.
He had recently withdrawn from the competitive graduate program in neuroscience at the University of Colorado Denver, where he was one of six pre-thesis Ph.D. students at its Neuroscience Program to be funded by a prestigious grant from the National Institutes of Health. The program of 35 students is dedicated to training outstanding neuroscientists and academicians who will make significant contributions to neurobiology, the university said in a statement.
In the first year of the five- to seven-year program, students take classes and complete three, three-month research rotations in the labs of different professors.
Professors who worked with him either did not return calls or declined to comment, saying police and university officials had told them not to speak to the media.
At one point in the year, Holmes was engaged in research about RNA and was to present a paper May 8 about RNA Biomarkers, according to a class schedule. It was unclear if he presented the paper.
Holmes recently took an intense, three-part oral exam that marks the end of the first year. Those who do well continue with their studies and shift to full-time research, while those who don't do well meet with advisers and discuss their options, including retaking the exam.
University officials would not say if he passed, citing privacy concerns.
The university said Holmes gave no reason for his withdrawal, a decision he made in June.
Holmes was not allowed access from the institution after his withdrawal, which was "standard operating procedure" because he was no longer affiliated with the school, Montgomery said. Holmes had no contact with university police, she said.
A resume posted on Monster.com paints a picture of a brilliant young man brimming with potential: He worked as a summer intern at the Salk Institute for Biological Studies in La Jolla in 2006 and mapped the neurons of Zebra finches and studied the flight muscles of hummingbirds while an undergraduate at the University of California, Riverside.
Ritchie Duong, a friend who has known Holmes for more than a decade, told the Los Angeles Times that in high school he liked to play cards and video games. They both attended undergraduate school at the University of California, Riverside, where they saw each other once a week to watch the TV show "Lost."
Duong last saw Holmes in December when they met for dinner in Los Angeles and saw a movie together. His friend seemed fine, he told the newspaper.
Academics came easily to Holmes both at high school and at the UC Riverside, Duong said.
"I had one college class with him, and he didn't even have to take notes or anything. He would just show up to class, sit there, and around test time he would always get an `A,'" said Duong, 24.
During the attack early Friday, Holmes set off gas canisters and used the military-style semiautomatic rifle, a shotgun and a pistol to open fire on the unsuspecting theater-goers, Oates said. Holmes had bought the weapons at local gun stores in the past two months. He recently purchased 6,000 rounds of ammunition over the Internet, the chief said.
The gun that jammed had a high-capacity ammunition magazine, according to the federal law enforcement official who spoke to The Associated Press on condition of anonymity in order to discuss the investigation. Police have said that a 100-round drum magazine was recovered at the scene and that such a device would be able to fire 50 to 60 rounds a minute.
The federal official spoke on condition of anonymity to in order to discuss the investigation, said the disabled weapon.
The Batman movie, the last in the trilogy starring Christian Bale, opened worldwide Friday with midnight showings in the U.S. "The Dark Knight Rises" earned $30.6 million in the midnight screenings, and, according to industry estimates, roughly $75 million on that day as a whole. That put it on track for a weekend total of around $160 million, which would be the second-highest opening weekend ever, following "The Avengers."
The shooting was the worst in the U.S. since the Nov. 5, 2009, attack at Fort Hood, Texas. An Army psychiatrist was charged with killing 13 soldiers and civilians and wounding more than two dozen others.
Across the street from the movie theater, a man who placed 15 crosses near Columbine High School after a 1999 massacre there has returned to Colorado with 12 crosses for the victims of Friday's shooting.
Greg Zanis, of Aurora, Ill., put up the 3 1/2-foot-tall crosses Sunday on a hill across the street from the Century 16 theater.
(Copyright 2012 by The Associated Press. All Rights Reserved.)