EL PASO — A 21-year-old gunman armed with a powerful rifle turned a crowded Walmart store in this majority-Hispanic border city into a scene of chaos and bloodshed on Saturday, stalking shoppers in the aisles in an attack that left at least 20 people dead and 26 others wounded, the authorities said.
For several minutes late on Saturday morning, the packed Walmart near the Cielo Vista Mall on the city’s East Side filled with gun smoke and the echo of gunfire. Workers and customers, some bloodied, fled out the doors. Others huddled in the aisles or on the ground.
“Texas grieves for the people of El Paso today,” the governor of Texas, Greg Abbott, told reporters. “On a day that would have been a normal day for someone to leisurely go shopping, turned into one of the most deadly days in the history of Texas.”
Manuel Uruchurtu, 20, had just paid at the cash register and was walking out of the store when he heard the sound of shots. He turned around and saw the gunman holding a long gun and wearing what looked like shoulder pads. As Mr. Uruchurtu fled the store, he saw two bodies on the ground outside, one surrounded by a pool of blood.
“I saw people crying: children, old people, all in shock,” he said. “I saw a baby, maybe 6 to 8 months old, with blood all over their belly.”
The authorities identified the gunman as Patrick Crusius, from a Dallas suburb. He was taken into custody after he surrendered to the police outside the Walmart. The authorities said they were investigating a manifesto Mr. Crusius, who is white, may have posted before the shooting, which described an attack in response to “the Hispanic invasion of Texas.”
“Right now, we have a manifesto from this individual,” El Paso’s police chief, Greg Allen, told reporters, though he said later that law enforcement officers were still not clear whether the gunman had posted the document.
The manifesto the chief appeared to be referring to was an anti-immigrant online screed titled “The Inconvenient Truth.” The post declares support for the gunman who killed 51 people in Christchurch, New Zealand; outlines fears about Hispanic people gaining power in the United States; and appears to discuss specific details about elements of the attack, including weapons. The four-page manifesto was posted on 8chan, an online forum where the Christchurch gunman also announced his attack. It appeared to have been published at 10:20 a.m., 19 minutes before the first 911 call, according to an archived version of the website.
“Hispanics will take control of the local and state government of my beloved Texas, changing policy to better suit their needs,” the manifesto said. It added that politicians of both parties are to blame for the United States “rotting from the inside out,” and that “the heavy Hispanic population in Texas will make us a Democrat stronghold.”
The shooting came six days after a gunman killed three people at a garlic festival in Gilroy, Calif. In that shooting, the gunman shot and killed himself after exchanging gunfire with the police. The massacre in El Paso was the deadliest American mass shooting since November 2017, when 26 people were killed in a church shooting in Sutherland Springs, Tex.
President Trump was briefed on the shooting, and administration officials said they were monitoring the situation. “Terrible shootings in El Paso, Texas,” Mr. Trump said on Twitter. “Reports are very bad, many killed.”
The president pledged “total support of Federal Government” to state and local authorities, and spoke about the shooting with Mr. Abbott, the governor, who headed to the scene of the attack on Saturday afternoon.
The city has had a binational feel because of its proximity and ties to its sister city in Mexico, Ciudad Juárez, and has been in the national spotlight for months. Thousands of Central American families have flooded the city and surrounding areas seeking asylum, overwhelming the Border Patrol and nonprofit groups working with immigrants.
The waves of migrants, and the difficulty the Trump administration has had providing shelter and medical care to them, has been a focus of Democratic lawmakers and Democratic presidential candidates in an election campaign in which immigration has become a central focus. But the city has also been home to generations of Mexican-Americans who consider themselves more Texan than Mexican. On a clear day, Mexico is visible from the shopping center parking lot.