Leading Democrats demanded the Trump administration act to curb white nationalists following the worst attack on Latinos in US history.
The US president was accused of stoking up the hatred with his rhetoric, including his vitriolic attack on four ethnic minority congresswomen last month.
It was this climate, Democrats said, which culminated in the carnage at a shopping mall in El Paso, Texas leaving 20 dead and 26 injured, of whom three are reported to be in a critical condition.
Attention focused to the threat posed by the far-right following the discovery a lengthy racist manifesto reportedly left by Patrick Crusius, 21, from Allen in Dallas Texas, the man named by US media outlets as suspected of being responsible for the slaughter.
District Attorney, Jaime Esparza, said that he would seek the death penalty for the suspect. John Bash, the US Attorney said the mass shooting was being treated as a domestic terrorism case.
The El Paso massacre was the third high profile attack linked to the far right in less than five years.
My heart is broken. For El Paso. For Dayton. For everyone who is impacted by the 40,000 gun deaths in our country every year. It’s on each and every one of us to end this crisis—and together, I still have faith that we will.— Beto O'Rourke (@BetoORourke) August 4, 2019
Last October 11 people died following a mass shooting at the Tree of Life Synagogue Squirrel Hill, Pittsburgh. According to a criminal complaint, Robert Bowers, 46, who is accused of the killings reportedly told a Swat officer he wanted all Jews to die.
In 2015 nine people were killed in an attack on a black church in Charleston, South Carolina. Dylann Roof, who was convicted of the multiple murders said he wanted to start a race war.
Presidential candidate Beto O’Rourke, who represented El Paso in Congress, rounded on Mr Trump.
"We've got to acknowledge the hatred, the open racism that we're seeing. There is an environment of it,” he said.
El Paso is a community that shows up for one another—on our best days and our worst. I met Rosemary’s family on the plane back to El Paso. They asked that we visit her and share her story. She was shot in the chest but is doing well after surgery. She’s strong—just like our city. pic.twitter.com/qjy4ecJOCw— Beto O'Rourke (@BetoORourke) August 4, 2019
“We see if from our commander-in-chief. He is encouraging this. He doesn't just tolerate it, he encourages it."
Pete Buttigieg, another Democratic candidate, added: “There is a need to stand up to white nationalist terrorism, we have to call it for what it is if we are going to fight it
“There is a need for a president who will stand up to white nationalist terror,” he said on CNN.
“There is a need to stand up to white nationalist terrorism, we have to call it for what it is if we are going to fight it.”
Our country is under attack from white nationalist terrorism, inspiring murder on our soil and abetted by weak gun laws. If we are serious about national security, we must summon the courage to name and defeat this evil.— Pete Buttigieg (@PeteButtigieg) August 3, 2019
But the White House acting chief of staff Mick Mulvaney denied Mr Trump’s was in any way responsible for the mass shootings when challenged over the president’s rhetoric.
"The president is just as saddened by this as you are, the president is just as angry about this as you, he wants to do something about this just as much as everybody else."
Richard Wiles, the El Paso County Sheriff, could not contain his anger and the shooting and the climate which made it possible.
“This Anglo man came here to kill Hispanics. I’m outraged and you should be too,” he said.
"This entire nation should be outraged. In this day and age, with all the serious issues we face, we are still confronted with people who will kill another for the sole reason of the colour of their skin.
“I fear things will not get better. Not pointing out anyone in particular, but I’m sick of people jumping in in front of the cameras offering prayers and condolences as things just keep getting worse.”
Most of the victims were shot in a Walmart store within the shopping complex before the shooter was detained at the scene, police said.
A CCTV image showing a man walking into the mall brandishing an assault rifle was released by police. He was wearing a dark T-shirt and ear protectors.
Greg Abbott, the Texas governor, said the state stood united in support of the victims and their families.
Various news reports said the ages of victims being treated at hospitals ranged from two to 82 years.
Police probe anti-immigrant manifesto
"The scene was a horrific one," said El Paso Police Chief Greg Allen, who added that many of the injured had life-threatening injuries.
He said police also had found an anti-immigrant manifesto that may have been written by Crusius and posted online - one reason it was being investigated as a hate crime.
"Right now we have a manifesto from this individual that indicates to some degree, it has a nexus to potential hate crime," Mr Allen said.
In the document, the author expressed support for the suspect in the Christchurch mosque shootings, in which 51 people were killed.
Asked during a CNN interview about reports of disturbing online posts made by the suspect, Texas Attorney General Ken Paxton said he would not be surprised in any way.
"I think those can help shed light on why he did it," Paxton said. "They are still interviewing him."
El Paso, a nine-hour drive from the Dallas area, lies on the Rio Grande River that marks the US border with Mexico. It has a population of 680,000, of which 83 percent are of Hispanic descent, according to US census figures.
Mexico's President Andres Manuel Lopez Obrador said three Mexicans were among the dead. Six Mexicans were wounded.
It was the eighth worst mass shooting in modern US history, after the 1984 shooting in San Ysidro that killed 21 people.
Trump reacts to shootings
In his first reaction to the shooting, Donald Trump, the US president, wrote on Twitter: “Terrible shootings in ElPaso, Texas. Reports are very bad, many killed. Working with State and Local authorities, and Law Enforcement. Spoke to Governor to pledge total support of Federal Government. God be with you all!”
He later called the attack "an act of cowardice".
Today’s shooting in El Paso, Texas, was not only tragic, it was 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....— Donald J. Trump (@realDonaldTrump) August 4, 2019
"Melania and I send our heartfelt thoughts and prayers to the great people of Texas."
It was initially reported that a man began shooting in the car park at the mall before moving inside.
One witness said he saw at least one person inside the store with a fatal head wound, and he saw shoppers in bloodied clothes.
Videos posted on social media showed customers at one store being evacuated with their hands up.
“We heard shots and saw smoke,” said Victor Gamboa, 18, who works at the McDonald’s inside the Walmart store where the shooting took place.
“I saw a man on the floor full of blood. He appeared to be dead. It happened very quickly.”
Returning to Washington from his golf club in Bedminster, New Jersey, Mr Trump promised action would be taken.
“A lot of things are being done right now as we speak.," said the US president.
"We have to get it stopped this has been going on for years, years and years in our country we have to get it stopped.
"A lot of things are in the works, a lot of good things."
'He was just shooting randomly'
Shoppers fled for their lives, including Kianna Long who was at the Walmart with her husband when they heard gunfire.
"People were panicking and running," Ms Long said. "They were running close to the floor, people were dropping on the floor."
She and her husband sprinted through a stock room at the back of the store before sheltering with other customers in a steel container in a shipping area.
“Hands up! Hands up!”— ABC News (@ABC) August 4, 2019
Videos show people being evacuated from the Cielo Vista Mall in El Paso, Texas amid the mass shooting at a Walmart that killed at least 20 people and left more than two dozen others injured. https://t.co/WG7XeQua9npic.twitter.com/tyuatkD2up
One woman, who gave her name as Vanessa, said she had just pulled into the Walmart parking lot when the shooting began.
"You could hear the pops, one right after another and at that point as I was turning, I saw a lady, seemed she was coming out of Walmart, headed to her car. She had her groceries in her cart and I saw her just fall," she told Fox News.
"He was just shooting randomly. It wasn't to any particular person. It was any that would cross paths."
Graphic video from the scene posted on social media showed what appeared to be dead bodies and wounded victims. Tales of heroism also emerged.
Officers said the mall was packed with back-to-school shoppers. El Paso police Sgt. Robert Gomez said the store was packed with as many as 3,000 people during the busy season.
In a statement, Walmart said: “We’re in shock over the tragic events at Cielo Vista mall in El Paso. We’re praying for the victims, the community and our associates, as well as the first responders.”
Oscar Collazo, a restaurant manager, said: “We never thought it would be so close to us this time. You see it on the news all the time, but you don’t think it could happen here until it does.”
In a statement, Mr Abbott said El Paso had been “struck by a heinous and senseless act of violence”.
“Our hearts go out to the victims of this horrific shooting and to the entire community in this time of loss,” he said.
El Paso, which has about 680,000 residents, is in west Texas across the border from Juarez, Mexico.
Local media said there was such an overwhelming response to an appeal by the police department for blood donations to help the wounded that long lines formed at medical centers, some of which had to tell would-be donors to come back on Sunday.
Some people handed out bottled water and slices of pizza to those still waiting in line.
Democrat candidates demand gun limits
Beto O’Rourke, the Democratic presidential candidate, abandoned a campaign event in Las Vegas to return to El Paso, 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,” he said.
El Paso is one of the strongest places in the world—and if there were ever a moment to be strong, it's this one. Strong for one another, for the families who have lost somebody, and for the first responders. Please go to https://t.co/ecw9y18OSP to support our community. pic.twitter.com/FFgLPbXNIY— Beto O'Rourke (@BetoORourke) August 3, 2019
The shooting took place within days of two people being shot and killed at a Walmart branch in Southaven Mississippi.
"It's not just today, it has happened several times this week. It's happened here in Las Vegas where some lunatic killed 50 some odd people," Vermont Sen. Bernie Sanders said as he and 18 other White House hopefuls were in Nevada to address the nation's largest public employees union.
"All over the world, people are looking at the United States and wondering what is going on? What is the mental health situation in America, where time after time, after time, after time, we're seeing indescribable horror."
Mr Sanders blasted Republican Senate leadership for being "more concerned about pleasing the NRA than listening to the vast majority of the American people" and said that Mr Trump has a responsibility to support commonsense gun safety legislation.
Former Vice President Joe Biden said he tried to call Mr O'Rourke and told reporters, "Enough is enough."
"This is a sickness," Mr Biden said. "This is beyond anything that we should be tolerating." He added: "We can beat the NRA. We can beat the gun manufacturers."
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 one of the largest bilingual, bi-national populations in the Western Hemisphere.
In recent months El Paso has also become one of the busiest entry points for undocumented migrants, especially from Central America, seeking asylum in the United States.
On a weekend the city attracts droves of shoppers from Mexico, including from its Mexican sister city Ciudad Juarez, population 1.5 million.