Police were stationed outside the courthouse where James Holmes, 24, made his first court appearance and deputies were positioned on the roof of the court building.
Holmes kept his eyes downcast and said nothing during the hearing at the Aurora courthouse that was attended by family members of some of the victims.
He looked sleepy and disoriented with dyed orange-red hair as he sat virtually motionless beside his lawyer in a maroon jailhouse jumpsuit wearing handcuffs. He remained silent throughout the hearing as the judge advised him of the case.
Holmes, who is expected to be formally charged next Monday, is being held on suspicion of first-degree murder and could face additional counts of aggravated assault and weapons violations. He has been assigned a public defender.
Holmes is accused of walking into a movie theatre on Friday in Aurora, a city of about 325,000, and armed with an assault rifle, a shotgun and at least one Glock pistol, opening fire on men, women and children at a midnight premiere of the Batman movie The Dark Knight Rises.
Soon after the shooting, there were reports of Holmes's hair being red and that he called himself "The Joker" when he was arrested. "The Joker" is one of Batman's fictional enemies and has brightly coloured hair.
Prosecutors said later they didn't know whether Holmes was on medication. His demeanour in court appeared to anger the relatives of some of the victims who attended the hearing. One woman's eyes welled up with tears. Two other women held hands tightly, one shaking her head.
Some stared at the suspect throughout the hearing, including Tom Teves, whose son, Alex, was killed in the shooting as he dove to protect his girlfriend. "I saw the coward in court today and Alex could have wiped the floor with him without breaking a sweat," said Teves.
District Attorney Carol Chambers said Monday her office is considering pursuing the death penalty against Holmes, but that decision will be made after consulting with the victims' families.
David Sanchez, who waited outside the courthouse during Holmes's hearing, said his pregnant daughter escaped uninjured but her husband was shot in the head and was in critical condition. "When it's your own daughter and she escaped death by mere seconds, I want to say it makes you angry," Sanchez said.
He said his daughter, Katie Medely, 21, and her husband, Caleb, 23, had been waiting for a year to watch the movie. Asked what punishment Holmes would be appropriate if convicted, Sanchez said, "I think death is."
After the court hearing, Chambers said "at this point, everyone is interested in a fair trial with a just outcome for everybody involved."
Holmes was arrested outside the theatre shortly after the mass shooting. He is being held in solitary confinement at a Denver-area county detention facility, said Aurora police Chief Dan Oates, and is not co-operating with police.
"He's not talking to us," Oates said.
A lawyer for Holmes's family told a San Diego news conference the family wanted privacy and did not want to discuss their relationship with the suspect.
Lisa Damiani said she would not reveal the family's whereabouts, citing concern she has for their safety. Damiani said it is important that the case be tried in a courtroom and not in the media.
"It's amazing how much support they are getting from their church," she said about the Holmes family.
Holmes quit school in June
Before the court appearance, new details emerged about Holmes's personal life.
Police have said 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.
Officials at the University of Colorado Anschutz Medical Campus were looking into whether Holmes used his position in a graduate program to collect hazardous materials.
It remained unclear whether Holmes's professors and other students at his 35-student Ph.D. program noticed anything unusual about his behaviour. His reasons for quitting the program in June also remained a mystery. Holmes recently took an intense oral exam that marks the end of the first year. University officials would not say if he passed, citing privacy concerns.
At a news conference, university officials refused to answer questions about Holmes. "To the best of our knowledge at this point, we think we did everything that we should have done," Donald Elliman, the university chancellor.
Officials also said the school received two suspicious packages Monday. The first package arrived early in the morning and was slipped under the door at a campus building while it was mostly empty. People were not allowed into the building until the threat was cleared. The second package was addressed to a person in a separate building and came to the school's central mail facility.
It's also now known that Holmes had applied to join an area gun club on June 25, saying that 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 heard a message on Holmes' voicemail that he described as "bizarre — guttural, freakish at best."
Rotkovich later told his staff not to accept him into the club, he said.
Meanwhile the pastor for the suspect's family said he was 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.
"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."
Obama visits Aurora
Monday's court hearing came a day after U.S. President Barack Obama travelled to Colorado to visit the victims' families and console a community reeling from a devastating loss.
"I come to them not so much as president as I do as a father and as a husband," Obama said afterward. "It was an opportunity for families to describe how wonderful their brother or their son or daughter was, and the lives that they had touched, and the dreams that they held for the future."
The president said he told the families that while the media spotlight is on the alleged perpetrator for now, eventually the shooter's presence in the collective mind will fade, and "what will be remembered are good people who were impacted by this tragedy."
Residents of the Denver suburb also came together Sunday to pray for the victims and their families.
A gospel choir sang as people gathered in a park outside Aurora's town hall, CBC's Lyndsay Duncombe reported. Some carried painted signs with the names of the victims, and many paused to wipe tears from their eyes.
Terri Sims sat under a tree with her sister and two young nieces. Sims told Duncombe she hasn't been able to sleep all weekend.
"Yesterday I was just crying all day, and my heart just goes out to everybody that was involved," she said.
Mayor Steve Hogan said people in Aurora were coming together "as a family would" and spoke of people inside the theatre who put their bodies in front of bullets to try and save others.
He thanked emergency workers who responded to the devastating shooting.
"It is the lives and acts of these heroes and the innumerable acts of kindness, love and care for our neighbours that defines who we are," the mayor said during Sunday's vigil.
Apartment cleared of explosives
Police who travelled to Holmes's apartment after his arrest found it rigged with explosives that were later cleared from the unit so law enforcement could safely enter and gather evidence.
The police chief said over the weekend that it could take months to determine a motive, noting that police are working with FBI behavioural analysts.
The tragedy has stirred memories of another Denver-area mass shooting, at Columbine High School in 1999, that left 12 students and one teacher dead.
Tom Mauser, the father of Daniel Mauser, one of the students killed at Columbine, has campaigned for more measures to prevent gun violence, but says his efforts haven't made any progress.
U.S. legislators are afraid to enact policies that might limit gun rights, Mauser said, because they believe, "'If something threatens our rights, our liberties, no we can't do that. Let's just punish the people who do bad. Let's be armed so we can try to stop them.'"
But Mauser believes that approach hasn't worked.
"Punishing them afterward is too late," he said.
The Aurora shooting is the worst in the U.S. since the Nov. 5, 2009, attack at Fort Hood, Texas, where an army psychiatrist was charged with killing 13 soldiers and civilians, and wounding more than two dozen others.Suggest a correction