Centennial, Colorado (CNN) James Holmes will spend the rest of his life in prison for killing 12 people and wounding 70 more at an Aurora, Colorado, movie theater.

A jury was unable Friday to reach a unanimous sentencing verdict, which results in life in prison without parole instead of the death penalty for Holmes, who had pleaded not guilty by reason of insanity in the 2012 shootings. He was convicted last month of 24 counts of first-degree murder -- two for each of the slain victims.

The 12-member jury reached a decision after deliberating almost seven hours since late Thursday. As they walked back into the courtroom shortly after 5 p.m. (7 p.m. ET), they made no eye contact with anyone. Some had a grim face. Some were ashen.

Holmes stood with his hands in his pockets as Judge Carlos Samour read the sentencing verdicts.

One female juror later told reporters that there was no way to resolve the disagreement on what the sentence should be.

"There was one firm holdout against the death penalty and two ... who were on the fence," said the juror, who would not give her name. "I don't know if they could have been swayed or not."

She said the graphic nature of the evidence made the 15-week trial very difficult. She called it a life-changing experience.

Emotional reaction from some

After the judge read on the first count that the jurors couldn't reach the unanimous decision required for the death penalty, Holmes' mother, Arlene, began crying and she put her head on her husband Robert's shoulder. She sagged into him and he held her up.

As the judge read on, several people in the area where family members and survivors had been sitting heeded the judge's prior admonition and left the courtroom instead of reacting emotionally.

Photos: Colorado shooting victims Photos: Colorado shooting victims Jonathan T. Blunk, 26, served for five years in the U.S. Navy. He died shielding a friend from the gunfire inside the theater. Hide Caption 1 of 12 Photos: Colorado shooting victims Alexander J. Boik, 18, was remembered by friends and loved ones as a "great person" whose "craziness touched hundreds," according to a Facebook page created in his memory. Hide Caption 2 of 12 Photos: Colorado shooting victims Air Force Staff Sgt. Jesse E. Childress, an Air Force reservist, was a cybersystems operator on active duty. He was 29. Hide Caption 3 of 12 Photos: Colorado shooting victims Gordon W. Cowden, 51, took his two teenage children to the theater. His children escaped unharmed. Hide Caption 4 of 12 Photos: Colorado shooting victims Jessica Ghawi, 24, was an aspiring sports reporter. She grew up in Texas before moving to Denver to try break into the television market there. Hide Caption 5 of 12 Photos: Colorado shooting victims Petty Officer 3rd Class John Thomas Larimer, 27, served in the Navy like his father and grandfather. He had been in the service for about a year. Hide Caption 6 of 12 Photos: Colorado shooting victims Matthew R. McQuinn, 27, died trying to provide cover for his girlfriend, Samantha Yowler, during the shooting, according to a family attorney. Yowler survived. Hide Caption 7 of 12 Photos: Colorado shooting victims Micayla C. Medek, 23, known to her friends as Cayla, was "very spiritual and close to God," cousin Anita Busch told CNN. Hide Caption 8 of 12 Photos: Colorado shooting victims Veronica Moser Sullivan, 6, was the youngest victim of the Aurora theater shooting. She had just learned how to swim. Hide Caption 9 of 12 Photos: Colorado shooting victims Alex M. Sullivan, 27, went to the movie to celebrate his birthday with his wife, two days before their first wedding anniversary. Hide Caption 10 of 12 Photos: Colorado shooting victims Alexander C. Teves, 24, recently graduated from the University of Denver with a master's degree in counseling psychology. He died protecting his girlfriend. Hide Caption 11 of 12 Photos: Colorado shooting victims Rebecca Ann Wingo, 32, joined the Air Force after high school, became fluent in Mandarin and served as a translator, according to CNN affiliate WFAA. Hide Caption 12 of 12

Ashley Moser, who is paralyzed and lost her 6-year-old daughter during the shooting, sobbed in her wheelchair and shook her head.

The verdicts took 11 minutes to read.

Lonnie Phillips, whose daughter Jessica Ghawi was killed, rubbed his wife Sandy's shoulder as she leaned forward, weeping. By the time the second charge including her daughter's name was read she had composed herself.

Holmes will not go to prison yet. Official sentencing was scheduled for August 24-26.

The same jury earlier convicted 27-year-old Holmes for the capital murder of 12 people.

They were: Jonathan Blunk, 26; Alexander Boik, 18; Jesse E. Childress, 29; Gordon Cowden, 51; Ghawi, 24; John Thomas Larimer, 27; Matthew McQuinn, 27; Micayla Medek, 23; Veronica Moser-Sullivan, 6; Alex M. Sullivan, 27; Alexander C. Teves, 24; Rebecca Ann Wingo, 32.

The jury also convicted him of attempted murder in the wounding of 70 more people.

DA believes he failed

Arapahoe County District Attorney George Brauchler told reporters outside the courthouse that he respects the outcome, even if he disagrees with it.

"As frustrated as I am at not achieving the result we wanted, those jurors did a hell of a job," he said. "I am disappointed at the outcome, I'm not disappointed with the system. I still think death is justice for what that guy did but the system said otherwise."

Brauchler said it was his fault that he couldn't get a death penalty result for the families.

Holmes' parents declined to speak to the media but issued a statement through an attorney.

"The Holmes family is unable to make any comment at this time other than to say that they are deeply sorry this has happened, and they are so sorry that the victims and families have suffered such tremendous loss," Lisa Damiani said in a press statement.

Sandy Phillips wore an emerald green pashmina shawl that belonged to her slain daughter. Phillips said that she and her husband have always said they didn't care whether the killer got life or death.

But "today what was hard for me was accepting (the sentences) for the others" who wanted to see Holmes die, she said.

"We didn't lose loved ones. Our loved ones were ripped from us. And they were slaughtered in that movie theater," she said. "But the jury chose another way and we have to accept that."

Robert Sullivan, grandfather of victim Veronica Moser Sullivan, found it hard to accept the jury's decision.

"That's not justice," he said angrily. "He's living, he's breathing. Our loved ones are gone."

Jury had rejected insanity defense

The shooting occurred during a midnight showing of a Batman movie, "The Dark Knight Rises," when Holmes burst into the theater through a rear door and opened fire.

Holmes' attorneys argued that their client is mentally ill and suffered a psychotic episode when he colored his hair orange-red, rigged his apartment with explosives, dressed in tactical gear and sprayed bullets into the theater under a cloak of darkness and tear gas.

In closing arguments Thursday, public defender Tamara Brady said the assault was a "tragedy" born of disease, not choice. The deaths cannot be answered by another death, and Holmes would be punished for the remainder of his days under a life sentence, she said.

Prosecutors, however, argued that Holmes should die for his crimes. His mental illness didn't prevent him from acting "rationally" elsewhere in his life, and the defendant must be held accountable for the mass murder, prosecutors said.

For Holmes, justice is his execution, Brauchler told the jury.

Holmes admitted to his crimes and had pleaded not guilty by reason of insanity.

But the jury rejected that defense in July, convicting him of a total of 165 counts, including the 24 charges of first-degree murder.

In the shooting, Holmes bought a ticket to see the Batman movie 12 days prior to the assault.

At the time, Holmes reportedly held a "human capital" credo that killing people would add value to his life. "You take away life, and your human capital is limitless," Holmes said in a chat message to his then-girlfriend months before the massacre.

Photos: Colorado movie theater massacre Photos: Colorado movie theater massacre The public gets its first glimpse of James Holmes, then 24, the suspect in the Colorado theater shooting during his initial court appearance July 23, 2012. With his hair dyed reddish-orange, Holmes, here with public defender Tamara Brady, showed little emotion. He is accused of opening fire in a movie theater July 20, 2012, in Aurora, Colorado, killing 12 people and wounding 70. Holmes faces 166 counts, almost all alleging murder or attempted murder. He has pleaded not guilty by reason of insanity. More photos: Mourning the victims of the Colorado theater massacre Hide Caption 1 of 45 Photos: Colorado movie theater massacre Police release the official photo from Holmes' booking after the shooting. Hide Caption 2 of 45 Photos: Colorado movie theater massacre Holmes often had a blank stare during his July 23, 2012, court appearance, seeming to be in a daze. Hide Caption 3 of 45 Photos: Colorado movie theater massacre Victims and their relatives and journalists watch the proceedings in 2012. Hide Caption 4 of 45 Photos: Colorado movie theater massacre Flags fly at half-staff on July 23, 2012, at the Arapahoe County Courthouse in Centennial, Colorado, where the movie theater shooting suspect had his first court appearance. The murder counts against Holmes carry a possible death penalty. Hide Caption 5 of 45 Photos: Colorado movie theater massacre Arapahoe County District Attorney Carol Chambers talks to reporters July 23, 2012, before heading into the courthouse. The murder counts against Holmes carry a possible death penalty. Hide Caption 6 of 45 Photos: Colorado movie theater massacre Family members of the victims arrive at the courthouse July 23, 2012, for the suspect's first court appearance. Hide Caption 7 of 45 Photos: Colorado movie theater massacre The Century Aurora 16 multiplex in Aurora becomes a place of horror after a gunman opened fire July 20, 2012, in a crowded theater. Hide Caption 8 of 45 Photos: Colorado movie theater massacre Holmes is accused of opening fire during a midnight screening of the Batman movie "The Dark Knight Rises." Holmes purchased four weapons and more than 6,000 rounds of ammunition, police say. Hide Caption 9 of 45 Photos: Colorado movie theater massacre Police investigate outside the Century 16 multiplex July 21, 2012, a day after the mass shooting. Hide Caption 10 of 45 Photos: Colorado movie theater massacre Agents search the suspect's car outside the theater. Hide Caption 11 of 45 Photos: Colorado movie theater massacre Aurora police escort a sand-filled dump truck containing improvised explosive devices removed from Holmes' booby-trapped apartment on July 21, 2012. Authorities have said they believe the suspect rigged his place before leaving for the movie theater. Hide Caption 12 of 45 Photos: Colorado movie theater massacre Police break a window at the suspect's apartment July 20, 2012, in Aurora. Hide Caption 13 of 45 Photos: Colorado movie theater massacre Law enforcement officers speak with Colorado Gov. John Hickenlooper, center, outside the suspect's apartment July 21, 2012. Hide Caption 14 of 45 Photos: Colorado movie theater massacre Law enforcement officers prepare to disarm the booby-trapped apartment July 21, 2012. Hide Caption 15 of 45 Photos: Colorado movie theater massacre Officials tow cars outside Holmes' apartment July 21, 2012. Police disassembled devices and trip wires set up in the apartment. Hide Caption 16 of 45 Photos: Colorado movie theater massacre Officers prepare to place an explosive device inside the apartment. Hide Caption 17 of 45 Photos: Colorado movie theater massacre Debris flies out a window, right, after law enforcement officers detonate an explosive device inside the apartment July 21, 2012. Hide Caption 18 of 45 Photos: Colorado movie theater massacre People mourn the victims during a vigil behind the theater where a gunman opened fire on moviegoers in Aurora. Hide Caption 19 of 45 Photos: Colorado movie theater massacre A woman grieves during a vigil for victims behind the theater. Hide Caption 20 of 45 Photos: Colorado movie theater massacre A distraught woman receives counseling from the Rev. Quincy Shannon, left, in front of Gateway High School in Aurora, where the families of the missing met after the shooting. Hide Caption 21 of 45 Photos: Colorado movie theater massacre Lin Gan of Aurora holds back tears as she speaks to reporters about her experience in the Century 16 theater. Hide Caption 22 of 45 Photos: Colorado movie theater massacre People embrace before a vigil for victims behind the theater where a gunman opened fire on moviegoers. Hide Caption 23 of 45 Photos: Colorado movie theater massacre Investigators work on evidence near the apartment of James Holmes on July 20, 2012. Hide Caption 24 of 45 Photos: Colorado movie theater massacre Members of the Aurora Police Department SWAT unit walk near the Holmes' apartment. Hide Caption 25 of 45 Photos: Colorado movie theater massacre Television news crews gather in front of the home of Robert and Arlene Holmes, parents of suspect James Holmes, in San Diego on July 21, 2012. Hide Caption 26 of 45 Photos: Colorado movie theater massacre A popcorn box lies on the ground outside the Century 16 movie theater. Hide Caption 27 of 45 Photos: Colorado movie theater massacre Adariah Legarreta, 4, is comforted by her grandmother Rita Abeyta near the Century 16 Theater in Aurora. Hide Caption 28 of 45 Photos: Colorado movie theater massacre Jessica Ghawi, an aspiring sportscaster, was one of the victims. Hide Caption 29 of 45 Photos: Colorado movie theater massacre A woman waits for news outside Gateway High School, a few blocks from the scene of the shooting at the Century Aurora 16. Hide Caption 30 of 45 Photos: Colorado movie theater massacre Aurora police chief Daniel J. Oates speaks at a press conference near the Century 16 Theater on July 20, 2012. Hide Caption 31 of 45 Photos: Colorado movie theater massacre Agents search the trash container outside the suspect's apartment in Aurora. Hide Caption 32 of 45 Photos: Colorado movie theater massacre A Federal ATF officer carries protective gear onsite at the home of the shooting suspect. Hide Caption 33 of 45 Photos: Colorado movie theater massacre President Obama speaks on the shootings at a July 20, 2012, event in Fort Myers, Florida. Hide Caption 34 of 45 Photos: Colorado movie theater massacre Moviegoers are interviewed at the Century Aurora 16. Hide Caption 35 of 45 Photos: Colorado movie theater massacre Officers gather at the theater July 20, 2012. Hide Caption 36 of 45 Photos: Colorado movie theater massacre Investigators were a common sight at the theater on July 20, 2012. Hide Caption 37 of 45 Photos: Colorado movie theater massacre Authorities gather at the shooting suspect's apartment building in Aurora. Police broke a second-floor window to look for explosives the suspect claimed were in the apartment. Hide Caption 38 of 45 Photos: Colorado movie theater massacre Screaming, panicked moviegoers scrambled to escape from the black-clad gunman, who wore a gas mask and randomly shot as he walked up the theater's steps, witnesses said. Hide Caption 39 of 45 Photos: Colorado movie theater massacre Onlookers gather outside the Century Aurora 16 theater. Hide Caption 40 of 45 Photos: Colorado movie theater massacre A woman sits on top of her car near the crime scene. Hide Caption 41 of 45 Photos: Colorado movie theater massacre Police block access to the Town Center mall after the shooting. Hide Caption 42 of 45 Photos: Colorado movie theater massacre Cell phone video taken by someone at the theater showed scores of people screaming and fleeing the building. Some, like this man, had blood on their clothes. Hide Caption 43 of 45 Photos: Colorado movie theater massacre Witnesses told KUSA the gunman kicked in an emergency exit door and threw a smoke bomb into the darkened theater before opening fire. Hide Caption 44 of 45 Photos: Colorado movie theater massacre What is believed to be the suspect's car is examined after the shooting. Hide Caption 45 of 45

If people were injured or maimed in the shooting, they amounted to "collateral damage," Holmes told a court-appointed psychiatrist after the shootings.

Like other patrons on July 19, 2012, Holmes walked into the theater No. 9 of Century Aurora 16 Multiplex Theater.

He then walked out a rear door, which he left propped open.

Just after midnight, about 18 minutes into the movie, he returned wearing a ballistic helmet, a gas mask, black gloves and protective gear for his legs, throat and groin.

A tear gas canister exploded in the theater, then gunfire rained from an AR-15 rifle, a 12-gauge shotgun and at least one .40-caliber handgun.

Holmes fled. But he was arrested in the parking lot outside the theater about seven minutes after the first 911 calls were made to police.