Nikolas Cruz (L) and his lawyer Melisa McNeill at his sentencing trial for the murders of 17 people at Marjory Stoneman Douglas High School in Parkland, Florida

Fort Lauderdale (United States) (AFP) - A US jury on Thursday rejected the death penalty and backed life imprisonment for Nikolas Cruz, who shot and killed 17 people at a Florida high school, in a sentence that shocked and angered some relatives of the victims.

Cruz, 24, wearing a striped sweater and large glasses, stared down expressionless at the defense table as the verdict was read while the parents of several slain children shook their heads in disbelief.

The jury deliberated for a full day on Wednesday and briefly on Thursday before deciding that Cruz should receive life in prison with no chance of parole for the February 2018 murders of 14 students and three staff members at Marjory Stoneman Douglas High School in Parkland, Florida.

A death penalty recommendation needed to be unanimous and one or more of the 12 jurors found it was not justified because of mitigating circumstances.

“I could not be more disappointed in what happened today,” said Fred Guttenberg, whose 14-year-old daughter Jaime died in the Valentine’s Day attack.

“I’m stunned. I’m devastated,” Guttenberg said. “There are 17 victims that did not receive justice today. This jury failed our families.”

Relatives of victims of the 2018 mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, at the sentencing trial for the gunman, Nikolas Cruz

Prosecutors and Cruz’s defense team gave their closing arguments on Tuesday after a three-month trial, during which the jury saw graphic footage of the attack and listened to harrowing testimony from survivors.

Lead prosecutor Michael Satz said Cruz, who pleaded guilty to the murders last year, carried out a “systematic massacre” and the appropriate penalty was death.

The 80-year-old Satz, who came out of retirement to try the case, ended his closing arguments by solemnly reciting the names of the 17 people who died.

- ‘Brain-damaged, mentally-ill’ -

Melisa McNeill, a lawyer for Cruz, urged the jurors to show compassion.

McNeill said Cruz was a troubled young man born with fetal alcohol stress disorder to a mother who struggled with homelessness, alcoholism and drug addiction before putting him up for adoption.

“He was doomed from the womb and in a civilized, humane society, do we kill brain-damaged, mentally ill, broken people?” McNeill asked in her closing statement. “Do we? I hope not.”

Gena Hoyer holds a photograph of her son, Luke, who was killed in the 2018 shooting at Marjory Stoneman Douglas High School in Parkland, Florida

Tony Montalto, whose 14-year-old daughter Gina was killed, said Cruz should not have been spared the death penalty just because he “had a tough time growing up.”

“This shooter did not deserve compassion,” Montalto said. “Did he show compassion to Gina when he put the weapon against her chest and chose to pull that trigger?”

Anne Ramsay, the mother of 17-year-old Helena Ramsay, said “the wrong verdict was given.”

“Even if this murderer had mental problems he still managed to get a gun,” Ramsay said. “He still managed to get an AR-15 and mow down our kids.”

Florida Governor Ron DeSantis expressed disappointment with the sentence.

“This stings,” DeSantis said. “It was not what I believe we were hoping for.”

On February 14, 2018, then-19-year-old Cruz walked into school carrying a semiautomatic rifle. He had been expelled a year earlier for disciplinary reasons.

In nine minutes, he killed 17 people and wounded another 17.

Cruz fled by mixing in with people frantically escaping the gory scene, but was arrested by police shortly after as he walked along the street.

- Gun control debate -

Debbie Hixon reaches out to her sister-in-law, Natalie Hixon, as the verdicts are announced in the trial of Parkland shooter Nikolas Cruz

The Parkland shooting stunned the nation and reignited debate on gun control since Cruz had legally purchased the gun he used despite his mental health issues.

On March 24, 2018, nationwide marches inspired by school shooting survivors and parents of victims brought together 1.5 million people – the largest public turnout ever in defense of stricter gun control laws in America.

But the Parkland attack prompted no significant reform by Congress and gun sales have continued to rise.

Thousands turned out following two other recent mass shootings: one at a Texas elementary school that killed 19 young children and two teachers, and another at a New York supermarket that left 10 Black people dead.

Those shootings helped galvanize support for the first significant bill on gun safety in decades, which President Joe Biden signed into law in June.

It included enhanced background checks for younger buyers and federal cash for states introducing “red flag” laws that allow courts to temporarily remove weapons from people who are considered a threat.

But the measure fell far short of an assault weapons ban sought by Biden.

In March, the Justice Department reached a $127.5 million settlement with survivors and relatives of Parkland victims who had accused the FBI of negligence for failing to act on tips received prior to the attack that Cruz was dangerous.