The death penalty trial for Parkland school shooter Nikolas Cruz has started. Opening statements began Monday, more than four years after Cruz killed 14 students and three staff members at Marjory Stoneman Douglas High School in Parkland, Florida. The criminal trial was supposed to begin in 2020, but the COVID-19 pandemic and legal fights delayed it. Cruz eventually pleaded guilty last October.

“I’m going to speak to you about the unspeakable,” Prosecutor Michael Satz said. “This defendant’s goal directed planned systematic murder, mass murder of 14 children, an athletic director, a teacher, and a coach.”

In this penalty phase, jurors will determine whether he should be sentenced to life in prison or receive the death penalty. A decision could take several months.

Satz named each person who was shot and wounded, while primarily referring to Cruz only as “the defendant.” He said Cruz had planned to be a school shooter long before the attack.

The statements included details ranging from the numerous times each victim was shot, the style of weapon and the number of ammunition cartridges Cruz carried, to his visit to a sandwich shop where he purchased a beverage after leaving the school.

Family members of the victims present in court shook their heads, some of them weeping, as Satz detailed the massacre.

Cruz, dressed in a gray-and-black sweater and wearing a black mask, was slumped over during much of Satz’s statement. He appeared to write several notes on paper and pass them to his lawyer.

Cruz, a 19-year-old expelled student with a history of mental health and behavioral problems at the time of the shooting, said in his guilty plea he was “very sorry” and asked to be given a chance to help others.

Prosecutors at the Broward State’s Attorney Office in arguing for the death penalty have noted in court documents that the shooting involving an AR-15 rifle was “cold, calculated and premeditated.”

The jury must be unanimous to recommend that the Parkland school shooter receive the death penalty. If any of the 12 jurors objects, Cruz will be sentenced to life in prison without parole.

Reuters contributed to this article.