A shooting at a supermarket in the US state of Texas that left 20 dead is being investigated as
Texas Walmart shooting: El Paso attack 'domestic terrorism'
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 prosecutors were "seriously" considering the federal charges.
The suspect 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 man, 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.
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. It lies along the Rio Grande across the border from Ciudad Juárez in Mexico.
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.
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. "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.
The attack came a few hours before another mass shooting in Dayton, Ohio and six days after a teenage gunman killed three people at a California food festival.