Twenty people were killed and more than two dozen injured in a shooting in a busy shopping centre in the Texas border town of El Paso, the state’s governor said.
Police said among the possibilities being investigated is whether it was a hate crime.
Two law enforcement officials identified the suspect taken into custody as 21-year-old Patrick Crusius of the Dallas area.
Police said another 26 people were injured, with most of the victims believed to have been shot at a Walmart near the Cielo Vista Mall.
The store was packed with as many as 3,000 people during the busy back-to-school shopping season.
“The scene was a horrific one,” said El Paso Police Chief Greg Allen, who added that many of the wounded had life-threatening injuries.
El Paso Mayor Dee Margo said police were investigating whether a document posted online shortly before the shooting was written by Crusius.
In it, the writer expresses concern that an influx of Hispanics into the United States will replace ageing white voters, potentially turning Texas blue in upcoming elections and swinging the White House to the Democrats.
The writer is also critical of Republicans for what he described as close ties to corporations and degradation of the environment.
Though a Twitter account that appears to belong to Crusius included pro-Trump posts praising the plan to build more border wall, the writer of the online document says his views on race pre-dated Mr Trump’s campaign and that any attempt to blame the president for his actions was “fake news”.
Although the writer denied he was a white supremacist, the document says “race mixing” is destroying the nation and recommends dividing the United States into territorial enclaves determined by race.
In the hours after the shooting, authorities blocked streets near a home in Allen, Dallas, associated with the suspect.
Officers appeared to speak briefly with a woman who answered the door of the grey stone house and later entered the residence.
Following the shooting, residents volunteered to give blood to the injured, while police and military members were trying to help people who were looking for missing loved ones.
“It’s chaos right now,” said Austin Johnson, an Army medic at nearby Fort Bliss, who volunteered to help at the shopping centre and later at the school that was serving as a reunification centre.
Adriana Quezada, 39, said she was in the women’s clothing section of Walmart with her two children when the shooting happened.
Now in the beautiful city of El Paso.
Texans grieve today for the people of this wonderful place.
We unite in support of all the victims.
We thank First Responders for their swift action.
We ask God to bind up the wounds of all who’ve been harmed. pic.twitter.com/2l8jDPHbe1
— Greg Abbott (@GregAbbott_TX) August 3, 2019
“I heard the shots but I thought they were hits, like roof construction,” she said.
Her 19-year-old daughter and 16-year-old son threw themselves to the ground, then ran out of the Walmart through an emergency exit. They were not hurt, Ms Quezada said.
The suspect, who used a rifle, was arrested without incident. Police believe he was the sole gunman but are continuing to investigate reports that others were involved.
The mass shooting in El Paso came less than a week after a gunman opened fire on a California food festival.
Santino William Legan, 19, killed three people and injured 13 others last Sunday at the popular Gilroy Garlic Festival, and died of a self-inflicted gunshot wound.
Ryan Mielke, a spokesman for University Medical Centre of El Paso, said 12 people were brought to the hospital with injuries, including one who died.
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
Two of the injured were children who were being transferred to El Paso Children’s Hospital, he said. He declined to provide additional details on the victims.
Eleven other victims were being treated at Del Sol Medical Centre, according to hospital spokesman Victor Guerrero. He said those victims’ ages ranged from 35 to 82.
Texas governor Greg Abbott called the shooting “a heinous and senseless act of violence” and said the state had deployed a number of law enforcement officers to the city.
“Reports are very bad, many killed,” US president Donald Trump tweeted.
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
Presidential candidate and former Texas congressman Beto O’Rourke appeared a bit shaken as he appeared at a candidate forum in Las Vegas, shortly after news of the shooting in his hometown was reported.
Mr O’Rourke, who said he had called his wife before going on stage, said the shooting shattered “any illusion that we have that progress is inevitable” on tackling gun violence.
El Paso, which has about 680,000 residents, is in West Texas and sits across the border from Juarez, Mexico.
The city has become a focal point of the immigration debates.
This is the 21st mass killing in the United States in 2019, and the fifth public mass shooting. Before today, 96 people had died in mass killings in 2019 — 26 of them in public mass shootings.