BOULDER, Colo. (AP) — Jurors on Friday began deliberating whether a mentally ill man who said he heard “killing voices” should be convicted of murder for fatally shooting 10 people at a Colorado supermarket in 2021 or be found not guilty by reason of insanity.

In closing arguments, prosecutors argued that Ahmad Alissa, who has schizophrenia, showed he was legally sane and knew the difference between right and wrong after amassing guns and ammunition to kill as many people as possible in the shooting in the college town of Boulder.

But defense lawyer Kathryn Herold told jurors that Alissa told state psychologists he heard voices that were yelling in his head, including what he described as “killing voices,” right before the shooting. The psychologists, who found Alissa sane at the time of the shooting, said he never provided details about the voices and whether they said anything specific. However, Alissa did tell them that he thought the voices might stop if he committed a mass shooting.

The experts thought the voices he was hearing played some role in the attack and they did not believe it would have happened if Alissa was not mentally ill.

Herold asked jurors to imagine what it was like to hear voices in your head, yelling in court: “Kill, kill, kill, kill!"

Mental illness is not the same as insanity under the law. In Colorado, insanity is defined as having a mental disease so severe it is impossible for a person to tell the difference between right and wrong.

The prosecution pointed to Alissa's actions the day of the shooting to show that he knew what he was doing. He used steel-piercing bullets and an optic sight that put a red dot on his victims, before firing multiple times at all but one of his victims, Assistant District Attorney Ken Kupfner said during closing arguments in Alissa's trial. Everyone he shot died in the attack.

Kupfner told jurors that Alissa fired his first shot at his second victim, Kevin Mahoney, in the parking lot after bracing himself on the hood of a car so he could take better aim with his semi-automatic pistol, which resembled an AR-15 rifle, Kupfner said. Alissa then pursued Mahoney and continued to shoot as he tried to get back to the store.

“The defendant was tenacious and he was relentless,” Kupfner said.

Herold accused prosecutors of trying to appeal to the emotions of jurors by presenting graphic videos of the attack and detailed testimony from victims, even though no one disputed Alissa was the shooter.

“When you remove that emotion, it is clear that insanity is the only explanation for this tragedy,” she told them.

Herold noted that the two state psychologists appointed by the court who found that Alissa was sane at the time of the attack had some reservations about their finding since Alissa did not share more information with them, even though that may helped his case.

She told jurors that they are the ones who must decide whether he was insane or not.

During two weeks of trial, the families of those killed saw surveillance and police body camera video of the shooting. Survivors testified about how they fled, helped others to safety and hid. An emergency room doctor crawled onto a shelf and hid among bags of chips.

Herold disputed comments that witnesses said Alissa made during the attack, including “This is fun,” arguing that was out of step with the lack of emotion the experts found when they met with Alissa. She said she thought their brains were trying to make sense of what had happened.

Several members of Alissa’s family, who immigrated to the United States from Syria, testified that starting a few years earlier he had become withdrawn and spoke less. He later began acting paranoid and showed signs of hearing voices, and his condition worsened after he got COVID-19 in late 2020, they said.

Alissa’s mother told the court that she thought her son was “sick.” His father testified that he thought Alissa could be possessed by a djin — an evil spirit — and that his condition was shameful for his family.

His parents and some of Alissa's siblings sat in the court gallery for the first time during the trial on Friday, just a few feet behind him. Alissa fidgeted during the arguments, sometimes appearing to be paying attention to the attorneys and other times appearing distracted and looking around the room.

Relatives of the victims mostly sat on the other side of the courtroom.

Alissa is charged with 10 counts of first-degree murder, multiple counts of attempted murder and other offenses, including having six high-capacity ammunition magazine devices banned in Colorado after previous mass shootings.

Alissa started shooting immediately after getting out of his car at the store on March 22, 2021, killing most of the victims in just over a minute. He killed a police officer who responded to the attack and then surrendered after another officer shot him in the leg.

Alissa got an adrenaline rush and a sense of power from shooting people, Kupfner argued, though prosecutors did not offer any motive for the attack. Kupfner said Alissa first began searching for public places like bars and restaurants in Boulder to attack, before focusing his research on large stores the day before the shooting. Alissa pulled into the first supermarket he encountered as he entered Boulder on his drive from his home in the Denver suburb of Arvada, he said.

The defense did not have to provide any evidence in the case and did not present any experts to say he was insane.