US authorities investigating what drove a young gunman from the Dallas area to kill 20 people at a Walmart store hundreds of miles away in the border city of El Paso said on Sunday they are treating it as a case of domestic terrorism.
Texas Governor Greg Abbott said Saturday's rampage appeared to be a hate crime, and police cited a manifesto they attributed to the suspect as evidence that the bloodshed was racially motivated.
A state prosecutor said they will seek the death penalty for the suspect, Patrick Crusius, 21, of Allen, Texas.
The US attorney for the western district of Texas, John Bash, said federal authorities were treating the massacre as a case of domestic terrorism.
"And we're going to do what we do to terrorists in this country, which is to deliver swift and certain justice," Bash told reporters at a news conference on Sunday.
He said the attack appeared "to be designed to intimidate a civilian population, to say the least."
The shooting reverberated on the US presidential campaign trail, with several Democratic candidates denouncing the rise of gun violence and repeating calls for tighter gun control measures.
At least two candidates, Mayor Pete Buttigieg of South Bend, Indiana, and El Paso native Beto O'Rourke, a former congressman, drew connections to a resurgence in white nationalism and xenophobic politics in the United States.
"America is under attack from homegrown white nationalist terrorism," Buttigieg said at a candidate forum in Las Vegas.
On Twitter, US President Donald Trump branded the shooting "an act of cowardice," adding, "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."
Police said the suspect opened fire with a rifle on shoppers, many of them bargain-hunting for back-to-school supplies, then surrendered to officers who confronted him outside the store.
El Paso Police Chief Greg Allen said the suspect was cooperating with investigators.
"He basically didn't hold anything back," Allen said at Sunday's news conference, but declined to elaborate.
The massacre came just six days after the last major outbreak of US gun violence in a public place - a food festival in California where a teenager killed three people with an assault rifle and injured a dozen others before taking his own life in a hail of police gunfire.
The Texas killings were followed just 13 hours later by another mass shooting in Dayton, Ohio, where a gunman in body armor killed nine people in less than a minute and wounded 27 others in the city's downtown historic district before he was shot dead by police.
SIGNS OF HATE
Crusius comes from Allen, Texas, a Dallas suburb some 650 miles (1,046 km) east of El Paso, which lies along the Rio Grande across the US-Mexico border from Ciudad Juarez.
A four-page statement posted on 8chan, an online message board often used by extremists, and believed to have been written by the suspect, called the Walmart attack "a response to the Hispanic invasion of Texas."
It also expressed for support for the gunman who killed 51 people at two mosques in Christchurch, New Zealand, in March.
El Paso and Ciudad Juarez, together with the neighboring city of Las Cruces, New Mexico, form a metropolitan border area of some 2.5 million residents constituting the largest bilingual, bi-national population in North America.
Amid reports on social media that some undocumented victims of the shooting might have been reluctant to seek medical aid, US Customs and Border Protection sought to put them at ease.
"We are not conducting enforcement operations at area hospitals, the family reunification center or shelters. We stand in support of our community," CBP West Texas said on Twitter.
Mexico's President Andres Manuel Lopez Obrador said three Mexican nationals were among the 20 people killed in the shooting, and nine others were among 26 victims who were wounded.
The carnage ranked as the eighth-deadliest mass shooting in modern US history, after a 1984 shooting in San Ysidro, California, that claimed 21 lives.
El Paso Mayor Dee Margo said police responded to the shooting within six minutes.
Local television station KTSM-TV published two photos it cited a law enforcement source as saying were security-camera images of the suspect as he entered the Walmart, wearing eyeglasses, khaki trousers and a dark T-shirt, and wielding an assault-style rifle. He appeared to be wearing headphones or ear protection.
Eyewitnesses described scenes of pandemonium as shoppers fled for their lives, including Kianna Long who was at the Walmart with her husband when they heard gunfire.
The couple sprinted through a stock room at the back of the store before huddling with other customers in a shipping area, she recounted. "People were panicking and running," Long said. "They were running close to the floor, people were dropping on the floor."
