DALLAS — In the days since a white former police officer was found guilty of murdering her unarmed black neighbor, unexpected after effects have inflamed emotions around the case:

First, the officer was sentenced to 10 years in prison, viewed by many critics as a lenient punishment for a convicted killer. Then, the officer received courtroom hugs from the judge and the victim’s brother, unusual public displays of forgiveness. And just days after the trial concluded, a key prosecution witness was killed, a death that police attribute to a drug deal gone bad, but that some residents speculate was retaliation for helping put a police officer behind bars.

On Tuesday, police announced two arrests for that death, but the cascade of events has continued to heighten distrust in a city where black and brown residents say their relationship with local police has always been frayed.

“Cops are not out here for black American people,” said Ifeanyi Buchunam, 31, who lives in the apartment complex where the witness, Joshua Brown, was killed. “They’re not out to protect us.”

The conviction of former Dallas police officer Amber Guyger, 31, for killing Botham Jean — a rare instance of police accountability for a civilian’s death — has triggered emotional fallout across this city, touching raw nerves on the issues of race, justice and power. The case achieved extraordinary dual outcomes: A white officer was convicted of killing an unarmed black man, but the process and its aftermath have further undermined faith in law enforcement for some.

“The trust in the police department is not there at all,” said Dominique Alexander, founder of the Next Generation Action Network, a local activist group. Like many black residents, he wants to see a federal investigation into Brown’s death, unconvinced that the Dallas Police Department has fully examined what was behind the 28-year-old’s killing.

“Of course, people are going to ask if Amber Guyger’s people did this to him. Or if a police supporter did this,” Alexander said. “And at the end of the day, as a community leader, I can’t say if they’re right or wrong.”

The department has insisted that Brown’s death has nothing to do with his testimony against Guyger.

“I assure you that is simply not true,” said Dallas Assistant Chief of Police Avery Moore during a news briefing Tuesday, criticizing officials and activists who have called for an independent investigation. “And I encourage those leaders to be mindful of their actions moving forward, because their words have jeopardized the integrity of the city of Dallas as well as the Dallas Police Department.” 

But the department’s integrity has long been in question for Dallas’s black residents, local leaders say, because of the history of police impunity.

For decades, Dallas’s police department was considered among the most brutal in the country, particularly in the black and Hispanic neighborhoods of South Dallas. A local news outlet reported in the 1980s that the department was involved in more fatal shootings per capita than many other major departments.

Those deaths included some particularly inflammatory cases: In 1973, an officer shot and killed a handcuffed 12-year-old Hispanic boy, Santos Rodriguez, who had been accused of stealing $8 from a vending machine; in 1986, an officer shot and killed Etta Collins, a black Sunday school teacher standing on her porch, who had called the police because she thought she heard a burglar.

In Rodriguez’s case, the officer served just 2½ years in prison. The officer who killed Collins was not indicted, according to the Associated Press.

Guyger’s “was the first trial since 1973 of a Dallas police officer in a fatal shooting,” said John Fullinwider, a longtime community activist in Dallas. “It’s been a period of almost complete unaccountability.”

The department has also endured painful loss . Amid nationwide uprisings over police excessive force, a peaceful protest in Dallas turned tragic in 2016 when a gunman killed five officers.

After the incident, the Dallas Police Department tweeted a photo of a black man openly carrying a rifle amid the protesters. “This is one of our suspects. Please help us find him!” the department tweeted.

The man, Mark Hughes, turned himself in, saying he was innocent and a supporter of Second Amendment rights.

“At the end of the day, the system is trying to get me,” Hughes said in an interview with CBS 11. The lone attacker had been killed at the scene after a standoff with police.

The department has been praised in recent years for taking some aggressive reform measures, but the checkered history has fueled questions about the fairness of Guyger’s trial and the handling of Brown’s death.

“If we didn’t have a lack of trust, people would never assume the department would be involved,” said Diane Ragsdale, a former Dallas council member who helped establish the local police review board. “There are consequences when you have a lack of trust. One of those consequences is: ‘I don’t believe what you say.’ ”

From the beginning, Guyger’s was an extraordinary case. The officer had been with the Dallas police for nearly five years, finished a shift and was still wearing her uniform when she opened the door to Jean’s apartment, believing it was her own, on Sept. 6, 2018. Guyger said she mistook Jean, 26, for an intruder and shot him.

Guyger’s trial was punctuated with dramatic, emotional moments, including Brown’s tearful testimony. Brown, who lived across the hall from Jean, said he heard Jean “singing every morning,” belting gospel music and Drake songs.

Then, as he sat in the witness stand, Brown paused, hunched over and wiped at his eyes with his pale green T-shirt. He testified that when he got home that night, he heard people meeting with what sounded like some surprise. Then two gunshots.

Brown said he saw Guyger come out and talk on the phone.

“She was crying,” he said. “Explaining what happened. What she thought happened. Saying she came into the wrong apartment.”

The testimony was key for the prosecution, said attorney Lee Merritt, who is representing Jean’s and Brown’s families.

“By testifying that he could hear Botham singing in his apartment he undermines a key element of the defense,” Merritt said in a Facebook post. “Amber claimed she shouted commands to Botham before shooting him. . . . No one heard that. No neighbors. No passerby’s. Not Joshua as he walked down the corridor. No one.”

Guyger was convicted and sentenced a week after Brown testified. Just days after that, Brown was fatally shot.

While Guyger’s trial was a welcome moment of accountability, Fullinwider said, it also exposed issues within the police department. Guyger’s partner admitted under oath to deleting text messages that she had sent to him, Fullinwider said, and details disclosed during the trial showed how closely the local police union had advised Guyger, even as the scene of the shooting remained active.

During the trial, an officer testified that he had tampered with police-car video after the shooting. There were questions about whether officers rendered adequate aid to Jean as he died.

“The trial provides these two windows into the department: misconduct and corruption,” Fullinwider said.

Dallas Police Chief U. Renee Hall called some of the revelations during the trial “disheartening” but “not reflective of the men and women of the Dallas Police Department.” During a news conference after the trial, Hall said the internal affairs division would investigate and pledged to make necessary changes.

A police spokesman said Thursday that Hall was unavailable for an interview.

Some residents say the skepticism about police involvement in Brown’s death is overblown. As he stood outside of the Southside Flats where Jean was killed, resident Tristan Smith on Wednesday morning said that he understands how Guyger ended up in the wrong apartment.

Smith lives down the hall from Jean’s apartment, on the fourth floor of a dimly lit building full of mazelike hallways. Smith said he has almost walked into the wrong apartment before, and two weeks after the shooting, a white man accidentally wandered into Smith’s apartment while he and some friends played dominoes, he said.

While Smith didn’t know Jean, he was an acquaintance of Brown, the murdered witness.

“His death didn’t have nothing to do with the case. People crying, ‘Oh, the police,’ that’s the dumbest thing,” said Smith, 30. “It’s no conspiracy, man. That dude was doing his thing and got caught up.”

The bizarre confluence of events involved in Guyger’s case makes it difficult to draw broader conclusions about the state of police accountability from the trial’s outcome, experts say.

While the number of officers charged with fatally killing people while on duty has ticked up in recent years, the increases are statistically insignificant, said Philip Stinson, a Bowling Green State University professor. Since 2005, when Stinson began tracking, 106 officers have been charged with murder or manslaughter for an on-duty shooting. Of that number, 36 have been convicted of crimes so far, often for lesser charges, such as misconduct.

Punishments for fatal shootings have ranged from no time in prison to four decades behind bars, according to Stinson.

Guyger’s shooting is not included in Stinson’s figures because she was off-duty at the time.

But critics assailed her 10-year sentence as insufficient, comparing it with lengthier punishments handed out to people for lesser crimes than murder.

“There’s no question in my view that that is an unfair sentence when you compare it to sentences meted out to people of color every day in this country,” said Christy Lopez, who ran the Justice Department group investigating police departments under the Obama administration. Harsh sentences should be addressed across the justice system, she added. “There’s a real need to recalibrate our sense of what a quote-unquote ‘right sentence’ is.”

Robert Rogers, an attorney for Guyger, said it’s a mistake to lump the case in with other officer-involved shootings.

“This was a 30-year-old woman who . . . shot what she thought was an intruder,” Rogers said. “She actually shot a truly innocent man who was absolutely doing nothing. And it was a storm of circumstances that you’ll never see again.”

Berman and Lowery reported from Washington. Julie Tate contributed to this report.