FORT LAUDERDALE, United States, (AFP) – A jury began deliberations on Wednesday over the fate of Nikolas Cruz, who shot and killed 17 people at a Florida high school in 2018, with prosecutors seeking the death penalty.

Cruz, now 24, pleaded guilty last year to the Valentine’s Day murder of 14 students and three staff at Marjory Stoneman Douglas High School in Parkland, a small city north of Miami.

The 12 person jury — seven men and five women — must decide between the death penalty, which would require a unanimous vote, and life in prison with no possibility of parole.

On Tuesday, prosecutors and Cruz’s defense team gave their closing arguments after a three-month trial, during which the jury saw graphic footage of the attack.

The lead prosecutor, Michael Satz, argued that Cruz should receive the death penalty as the shooting had been a “systematic massacre” planned months in advance.

Satz recounted the day of the attack in harrowing detail as Cruz kept his eyes down, and closed by reciting the names of the 17 people who died.

Melisa McNeill, a lawyer for Cruz, urged the jurors to show compassion for a troubled young man who was born with fetal alcohol stress disorder to a mother who struggled with homelessness, alcoholism and drug addiction, before he was adopted.

“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.”

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

In a matter of nine minutes, he killed 17 people and wounded over a dozen more.

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.

The shooting stunned the nation and reignited debate on gun control, since Cruz had legally purchased the gun he used.

Despite massive gun reform momentum prompted by the shooting, no significant national reforms were passed, and gun sales have continued to rise.

There have been more mass shootings, including one in May that left 19 young children and two adults dead at an elementary school in Uvalde, Texas.

After the latest shootings, Congress did pass legislation to increase funding for school security and mental health care.