US authorities are investigating a "hate-filled" online post they believe was published by the gunman who carried out a deadly attack in El Paso, Texas.

At least 20 people were killed and 26 injured in the shooting at a Walmart and nearby Cielo Vista shopping centre, in what turned out to be the first of two deadly gun attacks in the US over the weekend.

Two mass shootings hours apart kills 29 people

Sergeant Robert Gomez said the gunman, named by law enforcement officials in US media as 21-year-old Patrick Crusius, used a rifle in the attack.

FBI agents are looking into a post they are "reasonably confident" was published by the suspect shortly before the shooting.

Image: CCTV images apparently of the gunman have emerged

The four-page document, which was posted online, appears to describe the gunman's motives for the attack, and expresses extreme anti-immigrant and racist views, particularly against the Hispanic population.


It also mentions support of the shootings in Christchurch, New Zealand, in March, in which 51 people died after a gunman opened fire at two local mosques.

Speaking at a press conference, US representative Veronica Escobar said: "Not speaking about this particular incident, which is still under investigation, but the manifesto narrative is fuelled by hate, and it's fuelled by racism and bigotry and division."

El Paso police chief Greg Allen said that in examining the document, there was "potential nexus to a hate crime".

He described the scene of the attack as "horrific", adding that many of the wounded had life-threatening injuries.

Texas governor Greg Abbott confirmed 20 people had died in the attack, saying it was "one of the deadliest days" in the state's history. It is the eighth worst mass shooting in modern US history.

"This is disgusting, intolerable, it's not Texan, and we are going to aggressively prosecute it both as capital of murder but also as a hate crime - which is exactly what it appears to be without having seen all the evidence yet," he said.

Image: A suspect was detained over the shooting. Pic: Ayla Pequeno

Image: Police officers are seen inside the Cielo Vista Mall

At the time of the shooting, the supermarket was packed with up to 3,000 people, including many buying back-to-school supplies.

Officers said most of the victims had been shot at Walmart, adding that the mall had also been "secured".

A man in his 20s was detained near the El Paso mall. Police said they did not fire a shot.

Image: People were evacuated to a car park across from the Walmart store

Image: Shoppers left the area with their hands up after the mass shooting

During the attack, 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, saying that there was a shooter," she said. "They were running close to the floor, people were dropping on the floor."

Image: Kianna Long and her husband were caught up in the attack

The couple ran through a stock room at the back of the store before sheltering with other customers in a steel container.

Mexico's president Andres Manuel Lopez Obrador said three of those who died were from his country.

Doctors said 23 people had been taken to hospitals.

Image: At least 20 people were killed in the attack

The University Medical Centre of El Paso treated 12 patients, including two who were transferred to the El Paso Children's Hospital. Elsewhere, the Del Sol Medical Centre was treating 11 people.

One of the patients at the University Medical Centre of El Paso later died.

Multiple security forces were deployed to the scene of the attack, including police and state troopers as well as Homeland Security and border agents.

Image: Sergeant Robert Gomez updated reporters on the shooting

Police had urged people to stay away from the complex after receiving reports of multiple attackers at the mall.

But Sergeant Gomez said authorities had ruled out more gunmen being involved.

US President Donald Trump tweeted about the "terrible shootings" and pledged the support of the federal government to the state's governor.

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! — Donald J. Trump (@realDonaldTrump) August 3, 2019

Governor Abbott described the shooting as 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 in a statement.

"We have deployed troopers, special agents, Texas Rangers, tactical teams, and aircraft to the scene in a support role.

"The state of Texas will do everything it can to ensure justice is delivered to the perpetrators of this heinous act."

Image: Police urged people to stay away from the mall

Presidential candidate and former Texas congressman Beto O'Rourke said he was distraught by the news of the mass shooting in his hometown of El Paso.

Speaking to reporters in Las Vegas, he said he planned to return home immediately to be with his family and asked "for everyone's strength for El Paso right now... everyone's resolve to make sure that this does not continue to happen in this country."

Walmart said in a statement: "We're in shock over the tragic events at Cielo Vista Mall.

"We're praying for the victims, the community and our associates, as well as the first responders."

The mall complex is near Interstate 10 and on El Paso's east side.

El Paso, which has around 680,000 residents, is in West Texas and is located across the border from Juarez, Mexico.