An Army veteran, a 15-year-old boy and a hero mother were among 20 victims of Saturday's shooting at a Walmart in El Paso, Texas.

A gunman, identified by police as Patrick Crusius, opened fire on the crowded store in what authorities are calling an act of domestic terrorism.

The shooter targeted the super-store at the Cielo Vista Mall, a popular shopping destination for people both sides of the US-Mexico border.

Less than 20 minutes before the shooting, Crusius allegedly uploaded a twisted and seething anti-immigrant manifesto to an online forum outlining his sickening motives and revealing that he intended to target Hispanics.

At least 20 people were killed and 26 more were injured before Crusius was arrested.

Witnesses have told how Crusius displayed no expression as he fired at victims.

Witness Robert Jurado told the Washington Post: 'He was, like, all calm.

'He didn't show no remorse.'

Mexican authorities confirmed that seven Mexican nationals were among those killed.

Arturo Benavides

Arturo Benavides, 60, has been identified as one of the 20 people killed in Saturday's shooting at a Walmart in El Paso, Texas

US Army veteran Arturo Benavides, 60, had been shopping with his wife when gunfire erupted. She managed to escape, but her husband did not.

Several family members posted to social media over Saturday and Sunday looking for information about the man they knew as 'Turi'. They were heartbroken to learn that he was among the victims.

Benavides' niece, Jacklin Luna, described her uncle as 'a strong-willed, caring, giving, and special person' who well known in the community in the years he spent as a Sun Metro bus driver.

'He was the person to always give a helping hand, a home to stay, and a meal,' Luna told Buzzfeed of her uncle on Sunday.

'He loved each and every one of us in our own ways. Loved oldies on a Sunday morning, sitting out on his chair in the front porch with his dog Milo at his feet.'

Benavides' niece, Jacklin Luna (above together), described her uncle as 'a strong-willed, caring, giving, and special person' who well known in the community in the years he spent as a Sun Metro bus driver

Jordan and Andre Anchondo

Hero mom Jordan Anchondo, 25, was killed while shielding her two-month-old son from bullets.

She was shopping for back-to-school supplies when the attack happened.

Anchondo's heartbroken sister Leta Jamrowski said the mother-of-three fell on top of the infant as she was shot. The boy suffered broken bones and is being treated in a hospital.

'From the baby's injuries, they said that more than likely my sister was trying to shield him,' Jamrowski, 19, told the Associated Press.

'So when she got shot she was holding him and she fell on him, so that's why he broke some of his bones.

'He pretty much lived because she gave her life.'

Jordan's husband Andre was also killed in the attack, the family confirmed Sunday.

A friend recalled that he had recently turned his life around after struggles with drug dependence and run-ins with the law.

The friend, Koteiba "Koti" Azzam said: 'I love the guy. He had the character and the charisma..

Azzam said Anchondo had started a business in El Paso, building things from granite and stone, and made it successful through hard work.

He also was on the verge of completing a home he was building for his family.

In addition to their two-month-old son, the couple also share two daughters.

Jordan Anchondo, 25, was shot dead while shielding her two-month-old son (above together) from gunfire during the massacre

Anchondo's heartbroken sister Leta Jamrowski revealed she was among the 20 people killed. The 25-year-old victim is seen left and right in photos posted to social media

Jordan's husband Andre Anchondo (right) was also among the dead

Jordan and Andre Anchondo are seen in a wedding photo from a year ago

Andre Anchondo (above with his two daughters) is still missing as of Sunday afternoon

Angelina Englisbee

Angie Englisbee, an 86-year-old grandmother, was also killed, relatives told media.

Her son Will Englisbee told CNN that his brother last spoke to their mother by cell phone while she waited in line at Walmart, just minutes before the shooting.

Her granddaughter Mia told the New York Times that Angie had seven children and a son who died in infancy. She raised her children alone after her husband died of a heart attack.

Mia said: 'She was a very strong person, very blunt. It feels like hell — it doesn’t feel real.'

Angie Englisbee, an 86-year-old grandmother, was also killed

Javier Rodriguez

Javier Rodriguez, 15, was identified by his aunt, Elvira Rodriguez, on Sunday afternoon.

She shared a photo of the boy on Facebook asking for any information about her nephew, only to follow it up two hours later with a confirmation of his death.

'Thank you to everybody who helped us search for my nephew. We found him,' she wrote.

'I just don't get why ? I know I'll never have answers. I'm so confused, hurt, mad!!!!! May you Rest In Peace baby boy!!! We love you so much baby!!!!!'

15-year-old Javier Rodriguez (right), was identified by his aunt on Sunday

A relative shared this image of Javier Rodriguez after the shooting asking if anyone had seen him

Leonardo Campos

Leonardo Campos, Jr, was one of those killed in the attack, the Pharr-San Juan-Alamo school district said.

A statement to the Monitor said: 'The PSJA Family is sad to hear reports of the loss of one of our own, PSJA High School Class of 1996 Alum Leonardo Campos, Jr., during yesterday’s tragic shooting in El Paso'.

It is also thought that Campos' wife was killed in the attack.

A friend posted on Facebook: 'Leo, you were a great friend and always with a big heart. We are going to miss you brother.'

Leonardo Campos, Jr, was one of those killed in the attack, the Pharr-San Juan-Alamo school district said

Seven Mexican nationals

Mexican authorities confirmed that seven of their nationals were among those killed.

Mexican President Andrés Manuel López Obrador confirmed that six others were injured, including Mario de Alba Montes, 45, Olivia Mariscal Rodriguez, 44, and 10-year-old Erika de Alba Mariscal.

Those killed were:

Sara Esther Regalado and Adolfo Cerros Hernández

The children of Sara and Adolfo announced on Facebook that their parents had been killed in the attack.

The children of Sara and Adolfo announced on Facebook that their parents had been killed

Sara Esther Regalado (left) and Adolfo Cerros Hernández (right)

Gloria Irma Márquez

The family of Gloria Irma Marquez confirmed online that she had been killed.

They wrote online: 'Gloria was a dedicated mother, grandmother and friend.'

Gloria Irma Marquez was a mother and grand mother

Jorge Calvillo García

Jorge Calvillo Garcia, was confirmed among the dead by mayor Jorge Zermeño Infante of Torreón, Coahuila.

The mayor wrote on Facebook: 'God comfort his family and friends, as well as all those affected with this event.'

María Eugenia Legarreta Rothe

María Eugenia Legarreta Rothe, originally from Chihuahua, was confirmed killed by her sister, who wrote online: 'It's something I can't assimilate'.

María had reportedly gone to El Paso to pick her daughter up from the airport, but had stopped at Walmart to do some shopping first.

María Eugenia Legarreta Rothe was confirmed killed by her sister

Ivan Filiberto Manzano

Ivan Filiberto Manzano, of Ciudad Juarez, was confirmed killed by by Mexican authorities.

He had two children, aged five and nine.

Ivan Filiberto Manzano was a father of two

Elsa Mendoza de la Mora

Elsa Mendoza de la Mora, of the city of Yepomera, was a teacher and principal of Jaime Torres Bodet Elementary School.

She had gone into the Walmart to buy some items, while her husband and son waited in the car, her family told Mexican newspaper Milenio .

Former students described her as 'an excellent teacher loved by all'.

Elsa Mendoza de la Mora was among those killed, it was confirmed

The twenty-minute massacre was the eighth deadliest in US history.

Surveillance video shows a man believed to be Crusius walking in through the front entrance of the Cielo Vista Mall Walmart with an AK47-styled assault rifle.

The gunman, wearing what appears to be ear defenders and cargo pants, first opened fire in the parking lot outside the store, shooting and killing 'locals that were fundraising outside the Walmart selling water. Children and adults.'

He then walked through the front door in a calm and confident state, as if he was 'on a mission', a witness said.

Patrick Crusius allegedly confessed to opening fire on a Walmart in El Paso, Texas, on Saturday afternoon, killing 20 people and injuring 26 more. The 21-year-old from Allen, a Dallas suburb, has been described by those who knew him as a short-tempered 'loner' with long-held animosity toward Mexican immigrants. The suspect is seen left in a driver's license photo and right in the back of a police cruiser after his arrest