(CNN) The man suspected of killing 20 people and injuring 26 others in El Paso on Saturday may face hate crime charges in addition to capital murder charges, officials said.

Police say a racist, anti-immigrant document they believe was written by the 21-year-old white male suspect has a "nexus to a potential hate crime."

The four-page document posted online espouses white nationalist and racist views. It rails against immigrants and Hispanics, blaming immigrants and first-generation Americans for taking away jobs and for the blending of cultures in the US.

Federal authorities are treating the shooting as a case of domestic terrorism because the shooting "appears to be designed to intimidate a civilian population, to say the least," according to the US Attorney for the Western District of Texas, John Bash.

"We're going to do what we do to terrorists in this country, which is to deliver swift and certain justice," Bash said.

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