A man armed with an assault rifle has opened fire at a packed shopping area in El Paso, in the US state of Texas, killing at least 20 people and wounding 26 others, according to officials.
Authorities said on Saturday the suspect was arrested outside a Walmart store near the Cielo Vista Mall, eight kilometres from a border checkpoint with Mexico.
Police confirmed that a 21-year-old from Allen, Texas, was the only person in custody. US media identified the suspect as Patrick Wood Crusius, a white male. Police said he was believed to be the only shooter.
El Paso County records on Sunday showed Crusius was booked at the central jail in the city on capital murder charges. There was no immediate indication that he had an attorney.
Authorities said they were working to confirm whether a racist, anti-immigrant screed posted online shortly beforehand was written by the man arrested. The "manifesto" includes passages railing against the "Hispanic invasion" of Texas and the author makes clear that he expected to be killed during his attack.
The first sentence of the four-page document also expresses support for the gunman who opened fire at two New Zealand mosques in March, killing 51 people.
"Right now we have a manifesto from this individual that indicates to some degree, it has a nexus to potential hate crime," El Paso Police Chief Greg Allen said.
Speaking to reporters, Texas Governor Greg Abbott said: "Lives were taken who should still be with us today. Twenty innocent people from El Paso have lost their lives and more than two dozen more are injured."