SAN ANTONIO — Editor's note: The above video originally aired August 20.

The District Attorney's Office in El Paso has confirmed that a grand jury indicted Patrick Crusius Thursday morning on charges of capital murder.

Officials have ten days to assign his case to a court. El Paso prosecutors are seeking the death penalty.

Crusius, 21, is accused of carrying out one of the deadliest mass shootings in U.S. history. 22 people were killed and about two dozen were injured when a gunman opened fire inside an El Paso Walmart on August 3. 

Crusius emerged with his hands up from a vehicle that was stopped at an intersection shortly after last Saturday’s attack and told officers, “I’m the shooter,” Detective Adrian Garcia said in an arrest warrant affidavit. 

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Crusius later waived his Miranda rights and agreed to speak with detectives, telling them he entered the store with an AK-47 assault rifle and multiple magazines, and that he was targeting Mexicans.

Authorities believe that shortly before the attack, Crusius posted a racist screed online that railed against an influx of Hispanics into the U.S. The document parrots some of President Donald Trump’s divisive rhetoric about immigration, but the writer said his views predate Trump’s rise and that any attempt to blame the president for his actions was “fake news.”

Federal authorities plan to bring separate capital murder charges against the suspect.

The Associated Press contributed to this report.