(Reuters)

A judge in Boulder, Colorado, on Thursday (March 25) ordered a 21-year-old man accused of fatally shooting 10 people at a supermarket to be held without bail while he undergoes a mental health assessment requested by his lawyers.

Ahmad Al Aliwi Alissa faces 10 counts of murder and an attempted murder charge stemming from the rampage on Monday at King Soopers grocery store in Boulder, some 28 miles (45 km) northwest of Denver.

Appearing at a hearing in county court in Boulder, Alissa affirmed that he understood his rights under the law and understood that he would be held without bail, as ordered by Judge Thomas Mulvahill.

Prosecutors may file additional charges against Alissa in the coming weeks, District Attorney Michael Dougherty told the judge.

Defense lawyers for Alissa requested that the suspect undergo a full mental health assessment, which would likely push back his preliminary court hearing by a couple of months. Alissa waived his right to a preliminary hearing within 35 days to allow time for that assessment.

“We cannot do anything until we are able to fully assess Mr. Alissa’s mental illness,” Kathryn Herold, a defense attorney for Alissa, told the judge.

The bloodshed at King Soopers was the nation’s second mass shooting in less than a week, after a gunman fatally shot eight people at three Atlanta-area day spas on March 16.

The two attacks have reignited a national debate over gun rights and prompted President Joe Biden to call for new legislation from Congress. A bill intended to impose stricter background checks and ban certain types of semi-automatic rifles has stalled amid Republican opposition.

On Monday afternoon, Alissa arrived at the grocery store carrying a handgun and wearing a tactical vest, according to an affidavit.

Six days earlier, Alissa purchased a Ruger AR-556 pistol, a weapon that resembles a semi-automatic rifle, the affidavit said.

Police have not yet publicly identified a motive for the killings. Alissa, a naturalised US citizen from Syria who graduated from Arvada West High School in 2018, was described by his brother as antisocial and paranoid, the Daily Beast reported.

He pleaded guilty to third-degree assault for punching a classmate in late 2017.

The classmate and several witnesses said that attack was unprovoked, according to an Arvada Police Department incident report at the time. Alissa told an officer the classmate had called him a “terrorist” and racist names.