A shooting at a supermarket in the US state of Texas that left 20 dead is being investigated as domestic terrorism, officials say.
A 21-year-old white man was arrested where the attack took place in the city of El Paso, near the US-Mexico border.
He is believed to have posted an online document calling the attack a response to “the Hispanic invasion of Texas”.
The man could face federal hate crime and firearms charges which carry a death penalty.
The suspect opened fire on a crowded Walmart with an assault-style rifle and surrendered after being confronted by officers outside the store. Saturday’s attack also left 26 injured.
“We’re treating this as a domestic terrorist case,” US Attorney for the Western District of Texas John Bash told a news conference, saying the attack appeared “to be designed to intimidate a civilian population, to say the least”.
The man is believed to be the author of 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”, alluding to Hispanic people in the US.
The four-page document, reportedly 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.
The suspect, named by US media as Patrick Crusius, lived in Allen, in the Dallas area, about 650 miles (1,046km) east of El Paso. It is not yet clear how long before the attack he had gone to the city. He has been co-operating with investigators, police said, and reportedly told them he had acted alone.
The shooting, believed to be the eighth deadliest in modern US history, took place in a city where most of the population of 680,000 is of Hispanic descent.
The victims have not yet been named but Mexico’s President Andrés Manuel López Obrador said three Mexican nationals were among the dead.
CCTV images said to be of the attacker show an armed man in a dark T-shirt wearing eye glasses and what appears to be 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, and witnesses described scenes of chaos as customers fled for their lives.
“People were panicking and running, saying that there was a shooter,” Kianna Long 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.
‘They’re targeting us’
By Lauren Turner, BBC News, El Paso
“Yesterday I was in shock. Today, my heart is hurting.” Gilda Baeza Ortega is looking out at the Walmart in disbelief from across the car park. She had been on the way to the store then decided to go for breakfast with her parents instead.
But it is not just that that makes her feel so close to what has happened. “It’s the fact he was targeting us. I’m a Mexican-American and very proud of that. To me that is the biggest wound.”
People have been coming here all day to lay flowers, a cross, even a Rubik’s cube, in tribute. Some are also asking police when they can retrieve their cars from Walmart’s car park. It is a popular place for people to come shopping from Mexico and it means many now cannot make the return journey, their passports being locked in their vehicles.
Everyone talks of what a friendly place El Paso is, how everyone knows each other. A taxi driver mentions the “six degrees of separation” here. She is dreading the list of names coming out, worried she knows one of the victims.
US President Donald Trump called the attack “an act of cowardice” on Twitter: “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.”
On Sunday, he ordered flags to be flown at half-mast to mourn the victims in El Paso and Dayton.
Democratic presidential candidate Beto O’Rourke, an El Paso native, told CNN Mr Trump’s anti-immigrant rhetoric had stoked divisions: “He’s an open avowed racist and is encouraging more racism in this country.”
Also on CNN, New Jersey Senator Cory Booker, another Democratic presidential hopeful, said: “Donald Trump is responsible for this. He is responsible because he is stoking fears and hatred and bigotry.”
But acting White House Chief of Staff Mick Mulvaney rebutted the Democrats’ allegations and attributed the attacks to “sick” individuals, saying on ABC: “There’s no benefit here in trying to make this a political issue, this is a social issue and we need to address it as that.”
Mr Trump, who has made curbing illegal immigration one of the key points of his presidency, has previously made derogatory comments about Mexican migrants and has called large groups of migrants trying to reach the US an “invasion”.
In recent weeks, Mr Trump has been accused of racism after his attacks on members of Congress who are members of racial or ethnic minorities.
Growing far-right violence
By Gordon Corera, BBC security correspondent
The El Paso shooting fits a growing and disturbing trend of far-right violence internationally.
Like the attack in Christchurch, the suspected attacker fits a particular profile – an individual who may have acted alone but who inhabited an international online subculture of extremism, one in which others incite and encourage violent acts.
A document – which authorities have linked to the attacker – was posted online and was characteristic in its claims about population replacement (in New Zealand it was Muslims, in El Paso, Hispanics).
And again, as in Christchurch, just before he acted, the individual allegedly posted his intentions on the online free speech forum 8chan. The pressure may grow now to act against such platforms and also for the authorities to take this growing threat more seriously, especially in the US.