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Additional charges are expected to be filed against the suspect in the mass shooting at a grocery store in Boulder this week, including attempted first-degree murderColorado authorities announced Friday.

Boulder County District Attorney Michael Dougherty spoke on the steps of the Boulder Police Department to give an update on the next steps in the investigation and the upcoming trial of Ahmad Al Aliwi Alissa, who is accused of killing 10 people at the King Scoopers and injuring others. 

"It will be a lengthy court process," Dougherty told reporters. "In every murder prosecution, the process takes at least a year for us to complete. I anticipate that will be the same in this case." 

Ahmad Al Aliwi Alissa, 21, appears before Boulder District Court Judge Thomas Mulvahill at the Boulder County Justice Center in Boulder, Colo. on March 25, 2021. Three days after he was led away in handcuffs from a Boulder supermarket where 10 people were fatally shot, Alissa appeared in court for the first time and his defense lawyer asked for a mental health assessment "to address his mental illness." (Helen H. Richardson/The Denver Post via AP, Pool)

Dougherty and Boulder Police Chief Maris Herold praised the inter-agency cooperation and support in the investigation, which Herold called "complex" due to the scale of the crime scene. 

"It is heartening to see how the community supports this police department and the other victims involved in this unbelievable incident," Herold said. "For that, I want the community to know I am very grateful."

Alissa, 21, faces 10 counts of first-degree murder and one count of attempted murder after he was arrested Monday.

Dougherty revealed Friday that further charges will be filed against Alissa. No timeline was provided at the news conference, but the DA said the next court date will be announced in the coming week. 

No motive has been identified in the massacre, and the FBI is currently conducting a "deep-dive" into the suspect's background, Dougherty said. 

BOULDER SHOOTING SUSPECT AHMAD AL ALIWI ALISSA: WHAT WE KNOW

Alissa is being held without bail and was moved from Boulder County Jail to a correctional facility outside the county after jail staff learned of safety concerns and threats.

Alissa appeared during a brief hearing Thursday, only responding "yes" when asked if he understood his rights.

Defense attorneys for Alissa requested evidence and a witness list from prosecutors before asking the judge for a delay so they could assess their client's "mental illness."

Alissa did not enter a plea during the hearing.

BOULDER GROCERY STORE MASSACRE DESCRIBED BY WITNESSES AS CHAOS: HE JUST 'STARTED SHOOTING'

Police responded to a call around 2:40 p.m. local time Monday for a report of an active shooter.  The suspect was described as having a black AR-15-style gun and blue jeans.

Police have since confirmed that Alissa used a Ruger AR-556 in the shooting. He also had a 9mm pistol with him, which police believe he did not use. 

Multiple people described how the suspect shot at people inside and outside the store.

Ten people were killed. Victims ranged in age from 20 to 65 and included a veteran police officer, a store manager and a former photo director for various magazines.

BOULDER SHOOTING SUSPECT YELLED TO POLICE, 'I SURRENDER, I'M NAKED,' WITNESS SAYS

Eric Talley of the Boulder Police Department was the first officer to respond to the shooting; he was killed. The father of seven was hailed as a hero after 10 years of service with the department.

Other victims are Denny Stong, 20; Neven Stanisic, 23; Rikki Olds, 25; Tralona Bartkowiak, 49; Suzanne Fountain, 59; Teri Leiker, 51; Kevin Mahoney, 61; Lynn Murray, 62, and Jody Waters, 65.

Prosecutors have said they are awaiting evidence from police, who were still processing the King Scoopers grocery store crime scene as of Thursday.

Boulder County District Attorney Michael Dougherty said the suspect had lived "most of his life in the United States."

A Facebook page purported to belong to Alissa included messages criticizing former President Donald Trump’s response to immigration and refugees, along with personal gripes about not having a girlfriend.

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A former classmate described Alissa as "kind of scary to be around," while another described him as paranoid.

Police said Alissa did not answer officers’ questions when they first arrested him but he did ask to speak to his mother.

Fox News' Stephanie Pagones, Louis Casiano and Edmund DeMarche contributed to this report.