At a school board meeting this month in Uvalde, Texas, parents and administrators found themselves locked in what had become a familiar argument: Nearly a year had passed since a gunman breached Robb Elementary School and killed 19 children and two teachers. The community was still waiting for officials to fully disclose how it happened.

“Almost a year now, and honestly nothing has changed,” Jesse Rizo, the uncle of one of the massacre victims, told the board. “These people are pretty much begging you guys to answer questions. You came here and you pretty much oppress people. They ask you questions, you don’t have answers.”

Despite the passage of time, there is still strong disagreement over who should be fired for the slow police response to one of the worst school shootings in American history, and what position the town should take on the repeated calls from families of the victims to restrict guns. Neighbors who have known each other for years now find themselves unable to agree and more distant than ever before.

“We used to be a close community,” Mr. Rizo said after the school board meeting on May 15. “Now it’s like we don’t know each other anymore.”

United in grief in the weeks after the shooting that ignited a national firestorm over how the police respond to mass shootings, Uvalde in the painful months since then has drifted apart, dividing along fault lines that barely existed a year ago.

The fissures run deep and remain raw: between the victims’ relatives lobbying for stricter gun laws, and neighbors who have long been avid hunters and gun owners and bristle at any new restrictions; between supporters of the police, who are the subject of a district attorney’s investigation for their delay in taking down the gunman, and residents who now distrust law enforcement; between those still in mourning and those who would like to move on.

Frictions have occasionally spilled into the open in a city where everyone still shops at the same grocery stores, eats at the same restaurants, attends the same Little League games.

At a recent library event, residents pulled the city manager aside to ask, quietly, about when Uvalde could begin to put the shooting behind them, starting with finally getting rid of a makeshift shrine to the massacre’s victims that still fills the central plaza. “I’ve had more than one person ask me: When are you going to clean up the plaza?” said the city manager, Vince DiPiazza.

There have been overt displays of anger. The relatives of one of the children killed screamed at the mother of the 18-year-old gunman after running into her by chance on the street last year. A local pastor drew ire for defending the police during a school board meeting last summer. One person urged him to sit down, shouting, “Your time is up!”

“The negativity divides. You have everybody getting mad,” said Berlinda Arreola, the step-grandmother of one of the victims.

Disagreements and lingering resentments have complicated the preparations for Wednesday’s commemoration of the massacre. Officials urged outsiders to stay away from Uvalde, while relatives of some residents planned a memorial march through town.

Rifts have grown even among the families. Joe Alejandro, whose niece was killed, found himself disagreeing with other relatives who have been demanding stricter gun laws, such as raising the age from 18 to 21 to buy an AR-15-style rifle, the type used in last year’s massacre

“I’ve had guns all of my life, and my gun is not going to kill anybody,” Mr. Alejandro said. “This is how we grew up. You go hunting in the morning and go to school and the guns stay there,” he said, referring to his car. “Why come after me?”

Mr. Alejandro’s view is a common one in Uvalde, where voters in the majority Hispanic city surrounded by ranches and hunting land voted for Gov. Greg Abbott, a Republican, a little over five months after the shooting, in a race where his opponent, Beto O’Rourke, frequently wore a Uvalde baseball hat and had promised stronger gun control.

After more than 100 students walked out of classes last month as part of protests against gun violence, school administrators warned them that they would face consequences the next time.

Long after the gunfire, Uvalde remains on edge. Recently, the City Hall and a large supermarket went into lockdown after residents circulated images of a man walking around downtown with a gun on his shoulder. (It turned out to be a BB gun.) Some parents kept their children home from school during the final full week of classes this month amid social media threats of violence that turned out to be unfounded.

Tensions remain in part because several investigations into the shooting and police response remain unresolved.

An inquiry by the district attorney, Christina Mitchell, remains open into whether charges should be brought against any of the dozens of officers who waited for more than an hour to storm the classroom where the gunman was holed up with students and kill him. Ms. Mitchell has said that she intends to present any evidence of criminal wrongdoing to a grand jury. But such a presentation is likely still many months away.

“A case of this magnitude has to be deliberate, has to be thorough, and there cannot be haste,” she said in a statement. “Because I have seen cases that are quickly investigated and justice does not prevail in those cases.”

A medical study to determine whether a faster confrontation with the gunman could have saved any of the children has yet to be completed. The Justice Department, too, is still working on its inquiry into the police response. Vanita Gupta, the department’s third highest-ranking official, visited Uvalde last month to meet with officials and families and reassure them that the investigation was still happening, even if its results were not yet forthcoming.

The department has helped city officials connect with people in other cities torn apart by mass shootings, sharing a kind of grim new playbook for navigating the long, painful aftermath. “It reinforced in my mind that what was happening here is not unusual,” said Mr. DiPiazza.

Much of the frustration has been directed at school administrators, who oversee the school district’s small police force. The chief of that force, Pete Arredondo, was immediately singled out by the Texas Department of Public Safety’s director, Steve McCraw, for failing to swiftly confront the gunman.

But a report by a Texas House committee later found “systemic failures” in the police response, not just by Mr. Arredondo, but by other agencies, including the state D.P.S. and the city Police Department, which also participated in the response. Both Mr. Arredondo and a state police sergeant on scene, Juan Maldonado, were fired, and the officer who had been acting as the chief of the city Police Department at the time of the massacre resigned.

The school district revamped its Police Department, but the hiring of a new school police chief has not eased tensions. When a father of two students questioned the qualifications of a new police hire during a recent school board meeting, the district responded by barring him from school property for two years.

A letter signed by the new interim school superintendent, Gary Patterson, called the father’s actions disruptive and disturbing.

In addition to the school police chief, the district has hired three additional officers and hopes to bring in several more. “We’re being very careful and trying to hire the right type of person,” Mr. Patterson said in an interview. “Our Police Department is the most scrutinized in the world right now.”

The school building where the shooting took place now sits behind chain-link fencing, its windows boarded over, ready for a planned demolition. The sign at one corner of the campus has become a kind of shrine, visited by victims’ relatives and passing motorists, and students have been dispersed to other schools until a new facility can be built.

Before the shooting, the most prominent mural downtown had been the one bearing the town name, images from its history and its previous claim to Texas fame as “the honey capital of the world.” Now several streets and alleys are emblazoned with towering images of the fourth graders and their teachers who were killed, an unavoidable reminder of the city’s forever altered identity.

From the first hours after the shooting, it was clear that the massacre would test the closeness of the community. On the night of May 24, victims’ relatives had gathered at a hospital awaiting news of their children when the gunman’s mother walked in.

Her mother — the gunman’s grandmother — had been the first victim, shot in the face before the gunman drove to the school. She has since recovered.

Ms. Arreola, the step-grandmother of Amerie Jo Garza, who was killed, recalled feeling stunned as the gunman’s mother introduced herself. “I just wanted to let you know that it was my son who killed your kids, and I’m so sorry for this,” Ms. Arreola remembered her saying.

When Ms. Arreola and other relatives saw the woman on the street two months later, in July, Ms. Arreola became enraged. “What reason did he have?” she yelled, in a scene captured by a camera crew for the Spanish-language broadcaster Telemundo.

The gunman’s mother could be seen calling 911 asking for help, and also addressing the relatives. “I know my son was a coward, you don’t think I don’t know that?” she said. “You don’t think I’m carrying all that with me? I know. And I’m sorry.”

On a recent evening, scores of parents gathered to watch Little League games as the sun went down over a city park. Clouds slid by overhead, delivering a light drizzle.

“Life goes on,” said Lupe Leija, who works in construction and also serves on the league’s board. “But there’s still anger.”

He said his son was at Robb Elementary during the shooting and refused to sleep alone for two months after. Now, he said, his son and others were coming to the games, just trying to regain a sense of normality. “A lot of people come here to relax,” he said. “People just want to feel comfort. They want to feel peace.”

Under the lights, umpires call balls and strikes. Parents sit in folding chairs or stand and cheer for their children. Among them on some nights, Mr. Leija said, is the former state police sergeant, Mr. Maldonado. No one pays him much attention.

“He got released from his job,” Mr. Leija said. “What more do they want?”

Kirsten Noyes contributed research.