Crusius, 21, was booked at the downtown jail on capital murder charges, El Paso district attorney Jaime Esparza said Sunday.
"This community is rocked and shocked and saddened by what happened here yesterday, but we will proceed in an orderly fashion," Esparza told reporters.
Federal prosecutors have a "view toward" bringing federal hate crime and firearm charges against Crusius, John Bash, the United States attorney for the western district of Texas, added. The federal firearm charges could also carry a penalty of death.
Bash said authorities are treating the shooting, which "appears to be designed to intimidate a civilian population," as a case of domestic terrorism.
El Paso Police Chief Greg Allen said Saturday that authorities are examining what he called a "manifesto" that they believe was written by the shooter and shows a possible "nexus" to a hate crime.
After he was taken into custody, the suspect told investigators he wanted to shoot as many Mexicans as possible, two law enforcement officials told ABC News.
The officials also said an assault style rifle similar to an AK-47 and several magazines were secured at scene.
According to Texas state representative Jeff Leach, Crusius was a 2017 graduate from Plano Senior High School. He also attended Collin College from fall 2017 through spring 2019.
Collin College released the following statement on Twitter:
Police in Allen, Texas, said they'd had contact with Crusius on three different prior occasions that were "limited at best." In 2014, he was reported as a juvenile runaway but returned home shortly thereafter without incident. In 2016, he was a passenger on a Plano ISD school bus that was involved in an accident. Earlier this year, he called police to report a "false residential alarm" at his grandparents' home.
"There is no record of any person(s) ever contacting the Allen Police Department in reference to this suspect and any activity that he may have been engaged or involved in," police said.
At 10:39 a.m., police received a 911 call about an active shooter scene near the Cielo Vista Mall, which is near Interstate 10 on the east side of the city. It took six minutes from the time the first 911 call was placed until officers arrived on the scene.
That complex includes a large Walmart that was at-capacity during the back-to-school shopping season, according to local authorities.
Shortly after, Sgt. Enrique Carrillo, a police spokesman, said a suspect was in custody and there was no longer a danger to the public. The suspect, police said, surrendered to approaching El Paso officers without incident.
An eyewitness told ABC News in an interview that the shooter was dressed in cargo pants and wore ear protection. She said he began to fire in the parking lot and saw him shoot multiple people in cold blood.
From there, she said, the shooter walked into the store. She characterized his demeanor as calm and confident as though "he was on a mission."
El Paso Police Sgt. Robert Gomez said it did not appear that there were any additional suspects but cautioned that the investigation was still fluid.
The Associated Press and ABC News contributed to this report.