(CNN) — The gunman in the 2018 Parkland school massacre will be formally sentenced this week to life in prison -- but not until the families of those he killed have one more opportunity to face him in court.

After a monthslong trial to decide if Nikolas Cruz should be sentenced to death, a jury recommended he serve a life sentence without the possibility of parole for the shooting at a South Florida high school in which 17 people were killed, sparing his life after his defense attorneys argued he was a disturbed, mentally ill person.

Because jurors recommended life -- three voted against a death sentence, which in Florida must be unanimous -- Broward County Circuit Judge Elizabeth Scherer must abide by their decision when she sentences Cruz, 24, who pleaded guilty last year to 17 counts of murder and 17 counts of attempted murder.

Follow live updates: Parkland shooter Nikolas Cruz to be formally sentenced

Scherer is expected to issue a formal sentence Wednesday after the victims' loved ones, many of whom were disappointed and angered by the jury's sentencing recommendation, have another chance to take the stand starting Tuesday to testify about the impact of his actions.

The end of Cruz's trial comes just over a year after he pleaded guilty in connection with the Valentine's Day carnage at Marjory Stoneman Douglas High School, which catalyzed a nationwide call for gun control reform led by the shooting's teenage survivors and the victims' families. It remains the deadliest mass shooting at an American high school, even as the scourge of gun violence on US campuses continues; last week, a teacher and a student were killed in a shooting in St. Louis.

Many of the Parkland families already testified over several days this summer as prosecutors closed their case, describing the depth of the loss they had suffered. But those statements, according to the father of 14-year-old victim Jaime Guttenberg, who was among the 14 students killed, did not include everything the families wanted to say because they had to be vetted by attorneys on both sides.

"It wasn't the extent of how we feel," Fred Guttenberg told CNN last month after the jury's decision. "At the sentencing hearing, we will get to say whatever we want, including discussing how we feel now about this verdict."

The second round of victim impact testimony will happen over two days, with those who survived the shooting also entitled to speak, the Broward County State Attorney's Office confirmed to CNN in a statement. It's unclear how many of them or victims' loved ones will take the stand, but no time limits are being imposed, and some people may testify via video conference.

Victim impact statements this week do not need to be shown to the lawyers in advance, the state attorney's office said.

"I have a lot more I'd like to say. I have a lot more I'd like to say directly to the killer," Guttenberg told CNN, adding, "We will now get to tell him exactly how we feel about him."

Trial pit heinous crime against gunman's own history

Because of his plea, Cruz skipped the guilt phase of his trial and instead proceeded directly to the sentencing phase, in which prosecutors sought a death sentence while Cruz's appointed public defenders lobbied for life without parole.

To make their decisions, jurors heard prosecutors and defense attorneys argue for several months over aggravating factors and mitigating circumstances -- reasons Cruz should or should not be executed.

Prosecutors pointed to seven aggravating factors, including that the killings were especially heinous, atrocious or cruel, as well as cold, calculated and premeditated, backing their case with evidence the gunman spent months meticulously planning the shooting, modifying his AR-15 to improve his marksmanship and accumulating ammunition.

Prosecutors also presented Cruz's online search history showing how he sought information about past mass shootings, as well as comments he left on YouTube, sharing his express desire to perpetrate a mass killing.

"What one writes," lead prosecutor Michael Satz said during closing arguments, "what one says, is a window to someone's soul."

But defense attorneys said their client should be sentenced to life instead, pointing to a lifetime of struggles that began before he was even born: His biological mother, they said, used drugs and alcohol while pregnant with Cruz, causing a slew of mental and intellectual deficits that stemmed from fetal alcohol spectrum disorder.

Despite his issues -- and the educators and school counselors who were concerned about his behavior and poor academic performance -- Cruz never got adequate or appropriate intervention, defense attorneys argued. This was in part due to his late adoptive mother who, defense attorney Melisa McNeill said, "never truly appreciated" what was wrong with him.

"Sometimes," McNeill said in her own closing argument, "the people who deserve the least amount of compassion and grace and remorse are the ones who should get it."

Many families felt the jury failed them

In rendering their decision, the jury unanimously agreed the state had proven the aggravating factors beyond a reasonable doubt -- and they were sufficient to warrant a possible death sentence.

Ultimately, however, the jurors did not unanimously agree the aggravating factors outweighed the mitigating circumstances, resulting in a recommendation for life in prison and not death.

Three jurors voted against recommending the death sentence, jury foreman Benjamin Thomas told CNN affiliate WFOR -- a decision he disagreed with, noting: "I don't like how it turned out, but ... that's how the jury system works."

One of the jurors was a "hard 'no,'" who couldn't vote for death because she "didn't believe, because he was mentally ill, he should get the death penalty," Thomas said. Two more jurors joined her.

The woman was "not moving" from her stance, juror Melody Vanoy told CNN. "Whether we took 10 hours or five days" to deliberate, "she didn't feel she was going to be moved either way."

Vanoy herself voted for life, telling CNN she was persuaded because she "felt that the system failed" Cruz repeatedly throughout his life.

Regardless, the outcome did little for the families who hoped to see Cruz sentenced to death and who, in the hours after the jury's verdict was read, saw their disappointment turn to anger and confusion as they grappled with the jury's decision.

"I'm disgusted with those jurors," said Ilan Alhadeff, the father of student victim Alyssa Alhadeff. "I'm disgusted with the system, that you can allow 17 dead and 17 others shot and wounded, and not get the death penalty. What do we have the death penalty for?"

"This shooter did not deserve compassion," Tony Montalto, father of slain 14-yera-old Gina Montalto, said outside the courtroom after the jury's findings were read.

"Did he show the compassion to Gina when he put the weapon against her chest and chose to pull that trigger, or any of the other three times that he shot her? Was that compassionate?"

Not all the victims relatives felt that way. Before the end of the trial, Robert Schentrup, the brother of victim Carmen Schentrup, told CNN he was against the death penalty -- in Cruz's case and all others.

"Logically," he said, "it doesn't follow for me that we say, 'Murdering someone is this horrible, heinous, awful, terrible thing, and in order to prove that point, we're going to do it to someone else.'"

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