[Updated at 5:10 p.m. EST]

CENTENNIAL, Colo.--James Holmes, the suspect in the Colorado theater massacre, appeared in a Colorado courtroom on Monday, three days after one of the deadliest shooting sprees in modern American history.

Arapahoe County District Court Judge William B. Sylvester advised Holmes of his Miranda rights, and said that there was probable cause to continue to hold him without bond on suspicion of first-degree murder.

Holmes, who was transported from a holding cell to the courtroom via an underground tunnel, appeared dazed. His brow furrowed. His head bobbed. His eyes opened and closed often. His hair was dyed a cartoonish orange-red. His hands and feet were shackled. He did not speak.

[COMPLETE COVERAGE: Colorado theater shooting]

Seated in a jury box next to Tamara Brady, a public defender, Holmes never looked in the direction of a gallery that included victims and their advocates. Two sheriff's deputies stood watch nearby.

His demeanor, however, angered the relatives of some of the victims of the shooting. Some stared at him during the entire hearing, including Tom Teves, whose son, Alex, was killed in the attack. Teves watched Holmes intently, sizing him up.

"I saw the coward in court today and Alex could have wiped the floor with him without breaking a sweat," said Teves, whose son, a physical therapist, dove to protect his girlfriend. "You shot a 6-year-old. Come on give me a break. You're dressed in full combat gear, immediately surrender. Come on. Pick on some guys who know how to use guns," Teves told the AP.

The preliminary hearing lasted about 11 minutes. Holmes' next court appearance is July 30, when he is expected to be charged.

A decision on whether to seek the death penalty could be weeks or months away, District Attorney Carol Chambers told reporters as she entered the courthouse.

"It will be a conversation we have with the victims before we make that decision," Chambers said.

Holmes could also face additional counts of aggravated assault and weapons violations stemming from the mass shooting that killed 12 and injured 58 people at an Aurora, Colo., screening of "Dark Knight Rises."

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Clad in full body armor, he surrendered to officers in a parking lot behind the cinema. Holmes did not resist arrest, but investigators have since described the former Ph.D. student at the University of Colorado-Denver medical school as uncooperative.

Authorities and news reports have portrayed the native Californian as smart and shy, but no motive for the shooting spree has surfaced.

[SLIDESHOW: Colorado mourns victims]

Federal investigators were dispatched to assist local authorities with the investigation, but officials have indicated justice will be sought in a state courtroom.

Colorado has a death penalty, but only one inmate has been executed since 1977. Three inmates are currently on death row, according to the Death Penalty Information Center.

"If James Holmes isn't executed," former Denver prosecutor Craig Silverman told Reuters, "Colorado may as well throw away its death penalty law."

Despite the fact that Holmes was arrested with weapons on him—and his apartment found "booby-trapped"—Chambers said investigators are still diligently pursuing more evidence.

"I would say there's no such thing as a slam dunk case," she said during a press conference outside the courthouse. "It is a case where we are still looking at the enormous amount of evidence."

The district attorney, who admitted she was seeing the defendant for the first time, was asked if Holmes might have been on medication at the hearing.

"We have no information about that," Chambers said.

At a news conference in San Diego, where Holmes' family lives, their lawyer, Lisa Damiani, refused to answer questions about him and his relationship to the family. She said later: "Everyone's concerned" about the possibility of the death penalty.

When asked if they stood by Holmes, Damiani said, "Yes they do. He's their son."

All 110 seats in the courtroom were full for the hearing, with some 80 or so occupied by victims, their families or counselors recruited from local police departments to help those grieving. A few of the victims, some of them wearing dark sunglasses, embraced in long hugs before taking their seats.

Jessica Watts was in the court to represent her cousin, Jon Blunk, who was fatally shot in the theater after pushing his friend out of harm's way.

Watts held back her emotions when the alleged killer was ushered in, she told Yahoo! News.

"I tried not to have a reaction because I wanted the focus to be about Johnny," she said. "There's so many emotions that I have for him."

[The Associated Press and Yahoo News senior media reporter Dylan Stableford contributed to this report.]