Doug Stanglin and Aaron Martinez | USA TODAY

USA TODAY

EL PASO, Texas – The gunman accused of opening fire at an El Paso Walmart, killing 22 people, confessed to authorities that he had been targeting Mexicans, authorities say.

"I'm the shooter," Patrick Crusius, the 21-year-old suspect, told police upon surrendering to officers shortly after the attack near the Cielo Vista Mall, according to a statement by El Paso Detective Adrian Garcia in an arrest warrant.

Officers, who were responding to a disturbance report that was later updated to an active shooter call, initially found 19 people dead at the scene of the shooting, the affidavit states.

Michael Chow, The Arizona Republic via USA TODAY Network

Garcia said Crusius later waived his Miranda Rights and agreed to speak with officers about the assault on Saturday shoppers at the El Paso mall. In that confession, he said that he had targeted Mexicans, according to the documents.

Many of the dead, along with about two dozen others who were wounded, had Latino last names. Eight were Mexican nationals.

The white suspect, from a Dallas suburb, had driven 650 miles to El Paso, on the border, to mount the attack,using an AK-47, semi-automatic rifle with multiple magazines. He was arrested shortly after the attack when he stepped from his vehicle at a nearby intersection.

Authorities believe Crusius posted a racist online manifesto shortly before the rampage in which he decried the "invasion" of Hispanics into the U.S.

Crusius, who is being held without bond, has been charged with capital murder. Federal authorities are also weighing possible hate-crime charges.