CENTENNIAL, Colo. » A jury’s refusal to sentence Colorado theater shooter James Holmes to die for one of the worst massacres in U.S. history doesn’t mean the public is growing wary of capital punishment, because only a single juror blocked his execution, the lead prosecutor said Friday.

The lone holdout felt just as strongly that Holmes should get a life sentence as the 11 other jurors believed he should die for the 2012 shooting, District Attorney George Brauchler said, based on prosecution interviews with some of the panel. Twelve people were killed and 70 others injured in the attack.

"They were surprised, shocked that this juror held this view, and this view, this adamantly," he told The Associated Press in an interview one week after the jurors said they could not reach a unanimous verdict on each murder count. Their indecision automatically eliminated the death penalty for Holmes, who blamed the attack on schizophrenia and psychotic delusions. He will instead be sentenced to life in prison without parole.

The holdout hasn’t come forward to speak with prosecutors, but other jurors have said testimony about Holmes’ mental illness persuaded her to show mercy.

Death sentences in Colorado must be unanimous, and attorneys tell jurors that imposing death is their own personal, moral choice and to respect each other’s decisions.

The other jurors believed the holdout was strongly in favor of death until the end of their deliberations, when she revealed she was firmly in favor of a life sentence, Brauchler said.

When it was clear she wouldn’t budge, the jurors took a vote, and the holdout told them that if mental illness hadn’t been a part of Holmes’ defense, she too would have favored a death sentence, Brauchler said.

"It’s disappointing and frustrating," he said. "But to extrapolate any more from that one juror’s decision to not impose death is misguided."

The same jury swiftly rejected Holmes’ insanity defense, convicting him of 165 felony counts. And later, they swiftly agreed that his mental illness didn’t outweigh the heinousness of the attack, allowing the case to move closer to a death sentence.

Holmes’ attorneys have not spoken about the case, and Colorado Public Defender Douglas Wilson did not respond to several calls and emails seeking comment.

The case could have ended the same way more than two years ago, when Holmes offered to plead guilty if he could avoid the death penalty. But Brauchler said he would not accept it, in part because the defense refused to let Holmes be examined by a prosecution psychiatrist and would not provide the spiral notebook where Holmes scribbled detailed plans for the attack.

The victims and the public might not have ever learned in detail what was behind the shootings had the plea deal been accepted.

"This guy always intended to survive this, he intended to go to prison for life, and that did not seem to be a just outcome, to give him that without getting to know all the truth of this," Brauchler said. "The more truth we discovered, the more we realized a truth the community has to come to grips with too, and that’s that mental illness and evil are not mutually exclusive. They can coexist, and in this case they coexisted and evil dominated."

Prosecutor Lisa Teesch-Maguire said there were more than 1,200 victims and survivors involved in the case, though just 83 took the stand during the guilt phase. Prosecutors sought their input at every turn, including about whether to seek death, she said. They were almost evenly split. Some favored execution, while others feared the decades of appeals that accompany a death sentence.

Some favored life because they thought they would never actually see Holmes executed. Colorado has executed only one person in nearly half a century, and just three people sit on the state’s death row. The man closest to seeing his death sentence carried out was granted an indefinite reprieve in 2013 by the state’s Democratic governor.

The emotional, three-month trial that followed offered a rare look inside the mind of a mass shooter, as most are killed by police, kill themselves or plead guilty. Prosecutors were challenged to weave massive amounts of evidence and an outsized number of witnesses into a powerful narrative that would hold jurors’ attention while continually reminding them of the shooting’s human toll.

Brauchler and other members of the prosecution team said they had no regrets about their handling of the case.

"That being the case, it makes sense that if this was not going to result in death it would be because of a juror whose conscience kept them from doing what everyone else thought was the right thing," Brauchler said.