Aurora, Colo. - University of Colorado officials were looking Sunday into whether James

Holmes used his role in a graduate program there to amass an arsenal used in a theater shooting rampage, but school officials aren't saying whether they had any clue that he was anything more than a hard-working student.

Holmes, 24, was not cooperating with officials as he was being held in solitary confinement at a Denver-area county detention facility, Aurora Police Chief Dan Oates said.

"He lawyered up. He's not talking to us," the chief said.

It could be months before the motive behind the shootings that left 12 dead and 58 wounded is uncovered, with authorities working with FBI behavioral analysts and looking into Holmes' relationships.

Holmes is scheduled for an initial hearing today and has been assigned a public defender.

Police have said that Holmes began buying guns at Denver-area stores nearly two months before Friday's shooting and that he received at least 50 packages in four months at his home and at school. Also on Sunday, a gun range owner east of Denver said he recently rejected a membership application from Holmes in part because of a bizarre voicemail greeting on Holmes' phone.

Unanswered questions

While the University of Colorado disclosed that it was cooperating with police in the case, that disclosure was one of the few the university has made three days after the massacre. It remained unclear whether Holmes' professors and other students in 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.

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 whether he passed, citing privacy concerns. The university also 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, said Jacque Montgomery, a spokeswoman for the University of Colorado medical school. Holmes had no contact with university police, she said.

The university declined to release any details of Holmes' academic record, citing privacy concerns, and at least two dozen professors and other staff declined to speak with The Associated Press. Some said they were instructed not to talk publicly about Holmes in a blanket email sent to university employees.

Montgomery 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 program.

"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," he said.

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 that began in the early evening.

Obama said he told the families of the victims of Friday's massacre that "all of America and much of the world is thinking about them." He met with them at the University of Colorado Hospital in Aurora, which treated 23 of the people wounded in the mass shooting. Ten remain there, seven hurt critically.

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.

Meanwhile, 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."