The department “is committed to providing superior police service to the public in order to protect life,” Ms. Rubio said, her voice shaking. She recalled testifying before Congress to call for more gun control measures in the wake of mass shootings in her city. Then she looked up and her voice caught fire. “What I want no one can give me,” he said. “I want my daughter back. If I cannot have it, then those who have failed it will never know peace.” In the days after the massacre at Robb Elementary School, parents like Ms. Rubio and other relatives of the victims responded with shock and silent grief. Residents of this predominantly Mexican American community in South Texas turned inward and pushed outsiders away as they buried the dead and hugged each other during intimate family gatherings. But as time has passed and officials have largely failed to explain why it took officers more than an hour to confront the gunman who killed 19 children and two teachers, the shock has faded and the early anger has only intensified. In recent weeks, families have attacked their elected officials at City Council meetings. And on Sunday, hundreds marched through the city in their first collective call for accountability. The event, which organizers called the Unheard Voices March and Rally, started at the elementary school, still covered in flowers and photos of some of the 21 victims more than a month after the tragedy. Protesters braved the inclement weather, holding signs reading “Remember their names” and chanting “Save our children!” Once gathered at Uvalde Plaza, which has become an official gathering place for mourners, relatives of the fallen took turns reading the names of their loved ones aloud and recalling their shattered dreams of becoming baseball players and community leaders. Among those in attendance was Beto O’Rourke, the Democratic candidate for governor of Texas. Javier Cazares, whose 9-year-old daughter, Jackie, was killed in the shooting, said the seed for the rally was planted the day he stood over her body and vowed her death would not be in vain. “I want her name to be remembered,” Mr. Cazares said. “I promised her we would fight.” Mr Cazares said the families were demanding a detailed explanation of what happened during the May 24 response, and demanded that officials hold those responsible accountable. State Police Superintendent Steven McCraw called the response a “huge failure.” An official familiar with the inner workings of a Texas House investigative committee said lawmakers planned to release their findings in a private meeting with the families within a week or 10 days. Many of those who marched also want more than justice. Some families are pushing for stricter gun laws and background checks. But in a largely rural and socially conservative county, where gun culture has permeated everyday life and where many own guns for protection and hunting, gun control may prove an elusive goal, Mr. Cazares and others said. A US veteran and longtime gun owner, he once considered himself a staunch gun rights advocate. But something changed in him after the tragedy, he said in an interview. Mr. Cazares recalled in painful detail how he left his gun in his truck as he raced to his daughter’s school the moment he heard there was a gunman inside. Once there, he said, he begged armed officers to break in and take the gunman into custody. He later learned that his daughter was dead in a nearby hospital. A preliminary law enforcement report suggested officers waited about 78 minutes to enter classrooms where the gunman was terrorizing a teacher and children. Mr. Cazares said the memory of Jackie, who he described as a “cannon” who dreamed of one day visiting Paris, is what prompted him to take a full accounting and demand that the Uvalde school district beef up its security measures before the next school. year. “I’m not afraid to speak my mind and I will continue to do so so these families know they are not alone,” she said. Much of the anger in the community has focused on school police Chief Pete Arredondo, who was one of the first to arrive at Robb Elementary and, according to State Police, was the incident commander at the scene. He denied being in charge in an interview with The Texas Tribune and has since been placed on administrative leave from his position. He also resigned from a City Council seat he won before the shooting. Vincent Salazar, who lost his granddaughter Layla Marie Salazar in the massacre, came to the march wearing a black T-shirt with a picture of Layla wearing angel wings. He said he wanted the resignation of any officer who failed to breach the doors and stop the gunman in time. “If you’ve got a badge to protect people, protect babies, why didn’t they?” asked. “This is only the first step, the first course. This is far from over.” This anger was also seen in recent City Hall meetings. During a packed meeting in late June, Velma Lisa Duran, the sister of Irma Garcia, a teacher killed in the shooting, denounced the lack of transparency from authorities. Grieving families like hers, Ms. Duran said, were tired of “hearing empty words.” Visibly upset, she pointed out to the mayor the damage an automatic rifle, which was used by the gunman at Robb Elementary, could do to a body. “These children disappeared – my sister disappeared,” she said, adding that attending her sister’s funeral was a harrowing experience. “It was a closed coffin. I couldn’t hug her. I couldn’t touch her. I couldn’t say the last goodbye.” Holding back tears, she asked the mayor to explain why the officers in the hallway didn’t know that children who were constantly being attacked were constantly calling 911 begging for help. “There are a lot of kids who could have been saved,” he said. “This shouldn’t have happened. We are meeting after a massacre that took place. We need change. That’s enough.” The mayor, Don McLaughlin, tried to reassure Ms. Duran and other families that he felt “their pain.” “No, you don’t,” he replied curtly. Elsewhere in the meeting, Tina Quintanilla-Taylor, a local activist running for a school board seat in 2020, stood up, faced television cameras in the room and addressed politicians at the State Capitol. “Show your face,” Ms. Quintanilla-Taylor said. “Answer our questions. Now.” Days after the encounter, she recalled picking up her daughter from school moments before the attack. Ms Quintanilla-Taylor remains haunted by the sounds of gunfire as dozens of police officers waited outside. Now he feels an urgent need to continue speaking out for those who were lost. “We want accountability from all levels — local level, county level, state level, federal level,” she said in an interview. “I also want people to become more active. Register and vote.” He added that if officials were not responsive to people’s concerns, “vote them out.” Leonard Sandoval, who lost his grandson Xavier Lopez at Robb Elementary, believes he can change people’s minds through activism. Once a quiet family man, he has become outspoken about his desire for a total ban on assault weapons like the one used in Uvalde. It also supports uniform mass shooting tactical training for all levels of law enforcement. He has personally lobbied President Biden for more gun regulation and plans to participate in future marches to wake people up from apathy, he said, adding that a recent law passed by Congress aimed at preventing dangerous people from obtaining guns legally did not go far enough. At Sunday’s rally, Xavier’s mother, Felicha Lopez, took the microphone, surrounded by family members, and urged lawmakers at the State Capitol and in Washington to listen. “We’re asking for gun laws to be changed so they stop selling them to bad people,” Ms. Lopez said, her voice breaking. “Please change our laws so no more babies can be taken from us.” Rick Rojas contributed reporting. Kitty Bennett contributed to the research.