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 at the scene of the attack 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”.
As well as 20 counts of murder, he could face federal hate crime and firearms charges.
The gunman opened fire on a crowded Walmart with an assault-style rifle and surrendered after being confronted by police officers outside the store. Saturday morning’s attack also left 26 people injured.
“We’re treating this as a domestic terrorist case,” John Bash, the US Attorney for the Western District of Texas, told a news conference.
He said 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” in alluding to Hispanic people in the US.
The four-page document, reportedly posted some 20 minutes before police received the first emergency call from the Walmart, 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 say, and has reportedly told them he 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 six Mexican nationals were among the dead and seven others were injured.
Security camera images said to be of the attacker show an armed man in a dark T-shirt wearing eye glasses and what appear 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, police 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.
Some 13 hours later, a gunman opened fire in Dayton, Ohio, killing nine people, including his own sister.