Centennial, Colorado (CNN) -- The man accused of killing a dozen people in a shooting rampage at a Colorado movie theater had offered to plead guilty if authorities would spare his life.
But the prosecutor denied that request Monday, announcing that he will seek the state's highest punishment for shooting suspect James Holmes: the death penalty.
"It is my determination and my intention that in this case, for James Eagan Holmes, justice is death," Arapahoe County District Attorney George Brauchler said.
Speaking directly with dozens of victims' family members, Brauchler said, helped inform his choice.
Many of them watched the prosecutor announce his intentions in court Monday.
Bryan Beard, whose close friend was killed in the massacre, said one thought ran through his mind: "Thank goodness. I am so happy this is happening."
"The only way death will receive justice when somebody murders somebody else is death," Beard told CNN Denver affiliate KMGH-TV during a break in Monday's court proceedings. "I guess you fight fire with fire."
Beard told reporters that if Holmes is executed, he wants to attend.
"I've already said, give me a front-row ticket."
New trial date
But the legal wrangling in the case is just revving up, and Holmes' trial won't begin until next year.
The trial was originally scheduled for August, but a judge Monday pushed back the start date to February 3 and said it could be delayed further. Once it starts, the trial is expected to last four months.
Public defender Tamara Brady argued that it is important to provide enough time to present arguments in the case.
"Your honor, this case is the most important matter this courtroom and this courthouse will ever hear," she said. "They're trying to execute our client."
Prosecutors took the defense to task for publicly offering it, saying they hadn't been given enough information to even consider such a deal.
"Not only improper, but grossly improper," prosecutors said in a Thursday court filing. "For the intended purpose of generating predictable publicity."
The case against Holmes
Attorneys on both sides are under a gag order, leaving case watchers to divine tactics from court documents.
Federal agents have said the 25-year-old former University of Colorado doctoral student planned the attack for months.
Authorities said Holmes booby-trapped his apartment with explosives, then traveled to the movie theater in Aurora, Colorado, armed with weapons, tear gas and body armor. He planned to ambush audience members during a screening of "The Dark Knight Rises," authorities said, and he did.
Witnesses who spoke to CNN said the gunman roamed the theater, shooting randomly as people tried to scramble away or cowered between seats.
At the end of the July 20 rampage, 12 people were dead and 58 were wounded.
Tom Teves, the father of shooting victim Alex Teves, told CNN's Piers Morgan Live Monday night that he thinks Holmes should get the same mercy he showed his victims.
"I have no interest in understanding him," he said. "My interest would be to see him exterminated."
Attorneys prepare an insanity defense
Holmes faces 166 counts of murder and attempted murder for the shooting.
Last month, a judge entered a standard plea of not guilty for Holmes.
His parents sat among reporters in the courtroom during Monday's hearing. As the prosecutor announced his plans to pursue the death penalty, Holmes' father put his arm around his mother. Both of them rocked back and forth.
Holmes' attorneys have suggested they intend to pursue an insanity defense.
In the documents filed last Wednesday, his attorneys said they were still exploring a mental health defense, "and counsel will vigorously present and argue any and all appropriate defenses at a trial or sentencing proceeding, as necessary."
Peter Burns was outraged at the possibility of an insanity defense.
His friend, Jessica Ghawi, was among those killed in the movie theater shooting. Holmes' distracted appearance in court, he said, doesn't jibe with the details investigators have revealed about a man who they said created and executed a detailed, deadly plan.
"I think this is an act," Burns told CNN Monday. "I think this coward that shows up every day in court with this aloof look in his eyes that he's just spaced out -- well, I can't imagine somebody pulling off something like this to be in that case. I think as soon as he knows he goes into the courtroom, he knows exactly what's going on."
Burns said he wanted Holmes to receive the toughest punishment possible, but he questioned whether the death penalty -- with the lengthy court proceedings and appeals that come with it -- was the right approach.
"We want justice, but at the same time we want closure," he said. "Do we ever really get closure 17 years down the road?"
CNN's Jim Spellman and journalist Hunter Parsons reported from Centennial, Colorado. CNN's Catherine E. Shoichet reported from Atlanta. CNN's Ed Payne and Dana Ford contributed to this report.