The man accused of shooting dead 12 people in a Colorado movie theater made his first appearance in court on Monday, sitting silently in a red jailhouse jump suit and with his hair dyed bright red.

Formal charges against James Eagan Holmes, 24, will be filed on July 30, the judge presiding over the proceeding said. A public defender was appointed as his attorney.

Police say Holmes was dressed in body armor and toting three guns when he opened fire at a packed midnight screening of the new Batman movie early Friday. Fifty-eight people were wounded.

Arapahoe County District Attorney Carol Chambers will decide whether to seek the death penalty for Holmes. Chambers may not announce her plan at the hearing.

On Sunday, President Barack Obama traveled to Aurora, a Denver suburb of 325,000, to offer comfort to families of the victims. He told them their loved ones would be remembered long after the justice system was done with the killer.

Obama met with families in the University of Colorado Hospital, and in a televised address afterward he also did not mention the suspect's name.

He focused on the bravery of a young woman, Stephanie Davies, who saved her friend Allie Young by putting pressure on a gushing neck wound with one hand and calling for help on her cellphone with the other.

"They assure us that out of this darkness a brighter day is going to come," Obama said.

Holmes and his motives remained largely a mystery, with past associates saying he displayed no hints of a mental illness or violent tendencies.

He was armed with a Smith & Wesson M&P .223 semi-automatic rifle, similar to an AR-15 assault rifle, a 12-gauge shotgun and a Glock .40-caliber handgun. Police found an additional Glock .40-caliber handgun in his car. All the weapons had been bought legally.

He is in solitary confinement to protect him from other prisoners. Holmes had recently dropped out of a doctoral degree program in neuroscience at the University of Colorado's Anschutz Medical School, a few blocks from his apartment.