The man who fatally shot 10 people in 2021 at a Boulder, Colo., grocery store was found guilty of murder on Monday, with jurors rejecting his lawyers’ argument that mental illness made him unable to distinguish right from wrong.

The verdict followed about two weeks of testimony that focused on the mind-set of the gunman, Ahmad Al Aliwi Alissa, at the time of the shooting. Mr. Alissa, now 25, was diagnosed with schizophrenia after the attack; his lawyers admitted that he carried out the shooting, but said that he was so unwell at the time that he could not know that what he was doing was wrong.

The shooting on March 22, 2021, took place at a King Soopers supermarket, less than a week after another mass shooting, in Atlanta. The victims, ranging in age from 20 to 65, included the first police officer to arrive at the scene, store employees and shoppers.

Jurors deliberated for about six hours over two days before coming to their unanimous conclusion. Having been convicted of 10 counts of first-degree murder, including the murder of a police officer, Mr. Alissa by law must be sentenced to life in prison without the possibility of parole.

The judge said Mr. Alissa would be sentenced soon after the verdict on Monday.

Mr. Alissa, who has been in custody since the shooting, wore a striped dress shirt and khaki pants in court on Friday. He stood when the jurors entered and shook his head several times. While the guilty verdicts were being read, Mr. Alissa bit his nails and conferred with members of his defense team.

In addition to the 10 murder counts, Mr. Alissa was also convicted of a series of other charges, including 38 counts of attempted murder and six counts of possessing a large capacity gun magazine.

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