Shootings in El Paso and Ohio leave at least 29 dead.

The El Paso shooting is raising tensions in a city already on edge.

EL PASO — Residents of this city awoke on Sunday to the aftermath of a massacre in which a gunman opened fire in a crowded Walmart store, killing at least 20 people and injuring 26 others.

Officials were investigating whether the suspect in the killings, a white man in his 20s from Allen, Tex., was linked to a racist manifesto railing against immigration and the growing Hispanic population in Texas.

The attack is raising tensions in a predominantly Latino city that was already on edge over the federal government’s targeting of migrant families. Businesses closed around the city this weekend, sports events were canceled and congregants gathered for vigils.

In El Paso on Saturday night, more than 200 people gathered at St. Pius X church for a vigil for the victims and their families. “Any of us could be dead right now — that’s how close it feels,” said Celina Arias, 44, a schoolteacher who attended the vigil.

The shopping center was a regular destination for Mexican nationals.

The Walmart is less than 10 minutes’ drive from Bridge of the Americas linking El Paso and its sister city in Mexico, Ciudad Juárez, and is a regular destination for Mexican tourists who come to the city to shop and visit family. The two cities are bound by history, business and the extended families that live and work on either side of the border.

Rosa María Silva, 42, and Ivonne Moreno, also 42, both church employees in Ciudad Juárez, were on their way to shop at the Walmart on Saturday morning when they found their way blocked by police cars and ambulances. It was about 10:30 a.m., just after the shooting.

“We weren’t in there through a miracle of God,” Ms. Silva said. Ms. Moreno’s mother, who lives in El Paso, drove them to her house, and the three of them spent the rest of the day hunkered down, afraid to go out.

Only as dusk fell did the pair venture out to buy some snacks and head back over the bridge.

“It’s sad that there are people who discriminate so much,” said Ms. Silva. “But we aren’t going to judge everybody because of one person.”

Karen Peña, 19, who lives in El Paso and was crossing the bridge to visit her mother in Ciudad Juárez, saw a broader threat to the shooting. “I think it’s because of the migrants,” she said, referring to the Central American migrants who have been arriving at the southern border in record numbers. “It’s a warning to scare them off,” she said.

Elisabeth Malkin contributed reporting from El Paso.