A motive has not been determined in the mass shooting that killed 10 people at a Boulder, Colorado, grocery store, Boulder Police Chief Maris Herold said Friday.

It is also unclear why the specific King Soopers grocery store location was chosen, Herold added.

Boulder County District Attorney Michael Dougherty told reporters Friday, “I think the victims’ families and the community are desperate to know the motive. We want to know the motive and that’s going to be the focus of all our efforts going forward.”

The gun used in the Monday afternoon massacre was a semi-automatic Ruger AR-556 pistol that was bought legally in Colorado, Herold said. The suspect also had a 9mm handgun, which does not appear to be used in the shooting, he said.

The suspect, 21-year-old Ahmad Al Aliwi Alissa, was taken into custody about 50 minutes after the shooting was reported. He spent one night in the hospital for a leg wound before being booked into jail on Tuesday.

The officer who exchanged gunfire with the suspect was put on administrative leave per standard protocol, Herold said. Dougherty did not say if Alissa’s leg wound was from police gunfire.

Alissa was charged with 10 counts of first-degree murder as well as one count of attempted murder for allegedly shooting at a police officer who was not hurt. Dougherty said Friday that additional charges of attempted murder will be filed.

The district attorney commended the responding officers who he said saved lives by immediately charging into the store where they faced “a significant amount of gunfire.”

Alissa was first put on suicide watch when he was processed at the Boulder County Jail, which is protocol for high-profile suspects, Boulder County Sheriff’s Office spokesperson Carrie Haverfield told ABC News. But correctional officers there heard “rumblings” of threats against Alissa, so deputies took “proactive precautions” to ensure Alissa’s safety by moving him to an undisclosed facility outside the county, Haverfield said.

It’s unclear whether Alissa remains on suicide watch, but Haverfield said he is in “protective custody.”

Defense attorneys said in court Thursday that more time is needed to assess Alissa’s mental health. He was held without bail and the judge ordered a status conference to take place in about 60 to 90 days.

Dougherty said Friday that he hopes the trial will remain in Boulder.

One of the 10 people killed was Boulder police officer Eric Talley, who was the first member of law enforcement to arrive at the scene. Talley’s handcuffs were used to transport Alissa to jail, Boulder police said.

“Though this was a small gesture, we hope it is the start of the healing process that so many of us need at this time,” the police department tweeted.