A shooting at a supermarket in the US state of Texas that left 20 dead could have been a hate crime, officials say.
A 21-year-old white man was arrested at the Walmart store where the attack took place in the city of El Paso, near the US-Mexico border, on Saturday.
A document, apparently posted shortly before the attack and believed to have been written by the man, espoused white supremacist and racist views.
The tract called the attack a response to “the Hispanic invasion of Texas”.
The man, who opened fire with an assault-style rifle, lived in Allen, Dallas, about 650 miles (1,046km) east of El Paso, police said. The attack also left 26 injured.
Officials have not offered a precise motive for the attack, but El Paso Police Chief Greg Allen said investigators were looking into a document that could indicate a “potential nexus to a hate crime”.
He appeared to be referring to a text posted on 8chan, an online message board frequently used by the far right, which describes a “cultural and ethnic replacement brought on by an invasion”, in reference to Hispanic people in the US.
The four-page document, believed to have been posted some 20 minutes before police received the first emergency call, also expresses support for the gunman who killed 51 people in Christchurch, New Zealand, in March.
Police said the man, who surrendered after being confronted by officers outside the store, was still being interviewed. US media has named him as Patrick Crusius.
“We’re going to aggressively prosecute it both as capital murder but also as a hate crime, which is exactly what it appears to be,” Texas Governor Greg Abbott told reporters.
The shooting is believed to be the eighth deadliest in modern US history, and took place in El Paso, where the majority of the population is of Hispanic descent.
The victims have not yet been named but Mexican President Andrés Manuel López Obrador said three Mexican nationals were among the dead.
CCTV images said to be of the gunman and broadcast on US media show an armed man in a dark T-shirt wearing ear protectors.
Reports of an active shooter were received at 10:39 local time (16:39 GMT), and law enforcement officers were on the scene within six minutes, Mr Allen said.
The Walmart, near the Cielo Vista Mall, was full of shoppers buying back-to-school supplies at the time of the shooting.
“People were panicking and running, saying that there was a shooter,” Kianna Long, who was at the store, told Reuters news agency. “They were running close to the floor, people were dropping on the floor.”
Ms Long said she and her husband ran through a stock room before taking cover with other customers.
US President Donald Trump described the attack as “an act of cowardice”.
“I know that I stand with everyone in this country to condemn today’s hateful act. There are no reasons or excuses that will ever justify killing innocent people,” he wrote on Twitter.
Governor Abbott described it as “one of the most deadly days in the history of Texas”.
The shooting has led to an outpouring of sympathy, but also fresh calls for gun control.
The attack is the second deadly shooting to take place in a Walmart store this week, after an ex-employee of the company killed two former co-workers at a Mississippi branch on Tuesday.
Walmart’s CEO Doug McMillon posted on Instagram: “I can’t believe I’m sending a note like this twice in one week. My heart aches for the community in El Paso.”
Democratic presidential candidate Beto O’Rourke, an El Paso native, abandoned a campaign event in Las Vegas to return to his home town.
Earlier, he spoke at a labour forum, telling the crowd the shooting shattered any illusion that gun reform will “come of its own accord” in the US.
“We know that there’s a lot of injury, a lot of suffering in El Paso right now.”
Other Democratic presidential candidates also responded with calls for gun control.
New Jersey Senator Cory Booker was among them, saying the US seemed to be “accepting the idea that these [shootings] are going to be a regular occurrence”.
Texas Attorney General Ken Paxton, however, said gun control would probably not have stopped the attack.
He added that if a “crazy” gunman launched such an attack, there was no way that law enforcement officers could be there to stop it.
“The best way is to be prepared to defend yourself,” he told CBS News.
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