US Batman suspect mum as he heads to court

Amid the continuing investigation of Batman killer Holmes and his background, it has been a day for healing and remembrance in Aurora.

The gunman in the Colorado cinema massacre is refusing to co-operate and investigators say it could take months to learn what prompted the Batman film premiere attack.

James Holmes, 24, is due to appear in court at 0930 (0130 AEST) on Monday morning.

He will face charges of first-degree murder after opening fire on Friday at a cinema in Aurora, Colorado, during a midnight premiere of the latest Batman film and killing 12 people and wounding 58 others, some critically.

Holmes has been held in solitary confinement since his arrest.

He has been assigned a public defender and Aurora Police Chief Dan Oates said that the former doctoral student has "lawyered up".

"He's not talking to us."

Officials at the University of Colorado Anschutz Medical Campus were not saying whether they knew he was anything more than a hard-working student.

His reasons for quitting a PhD program in June remained a mystery.

The university declined to release details of his academic record, citing privacy concerns, and at least two dozen professors and other staff declined to speak with The Associated Press.

The university took down the website for its graduate neuroscience program on Saturday.

Amid the continuing investigation, Sunday was a day for healing and remembrance in Aurora, with the community holding a prayer vigil and with President Barack Obama arriving to visit families of the victims.

Obama said he told the families that "all of America and much of the world is thinking about them".

Congregations across Colorado prayed for the shooting victims and their relatives. Elderly churchgoers at an aging Presbyterian church within walking distance near Holmes's apartment joined in prayer, though none had ever met him.

Several thousand gathered for healing at the vigil on Sunday night, where a banner said: "Angels Walk With Those Who Grieve."

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 behaviour and a "bizarre" message on his voice mail.

When owner Glenn Rotkovich phoned to invite him to a mandatory orientation the following week, he said he heard a message on the voice mail that was "bizarre - guttural, freakish at best".

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.

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 weekly to watch the TV show Lost.

Duong last saw Holmes in December when they met for dinner in Los Angeles and saw a movie. His friend seemed fine, he told the newspaper. Academics came easily to Holmes both at high school and university, 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.

The pastor for the Holmes family recalled a shy boy who was driven to succeed academically.

"He wasn't an extrovert at all. If there was any conversation, it would be because I initiated it, not because he did," said Jerald Borgie, senior pastor of Penasquitos Lutheran Church. Borgie said he never saw the suspect mingle with others his age at church. He last spoke with Holmes about six years ago.

"He had some goals. He wanted to succeed, he wanted to go out, and he wanted to be the best," Borgie said. "He took pride in his academic abilities. A good student. He didn't brag about it."

During the attack, Holmes allegedly set off gas canisters and used a semiautomatic rifle, a shotgun and a pistol to open fire on theatre-goers, Oates said.

Holmes had bought the weapons at local gun stores in the past two months. He recently purchased 6000 rounds of ammunition over the internet.

The gunman's semiautomatic assault rifle jammed during the attack, forcing him to switch to another weapon with less firepower, a federal law enforcement official told The Associated Press. That malfunction and weapons switch might have saved some lives.

Oates said a 100-round ammunition drum was found in the cinema but said he did not know whether it jammed or emptied.

Investigators found a Batman mask inside Holmes's apartment after they finished clearing the home of booby traps and ammunition, a law enforcement official close to the investigation said.

The shooting was the worst in the US since the 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 cinema, Greg Zanis, of Aurora, Illinois, who placed 15 crosses near Columbine High School after a 1999 massacre there, returned to Colorado with 12 crosses.