Dallas police officer Amber Guyger has been fired after the fatal shooting of Botham Jean, an unarmed black man in his apartment.

On Sept. 6, Guyger returned to her apartment complex after a shift, entered the wrong unit — exactly one floor above her own — and shot and killed 26-year-old Jean, according to her arrest affidavit. Guyger said she mistook the apartment for her own and thought Jean was an intruder; Jean’s family lawyer has said the officer’s statement is “demonstrably false.”

Guyger was arrested and charged with manslaughter in Jean’s death in the days after the shooting, but she had remained on the city’s payroll on administrative leave. Her continued employment brought protests and harsh criticism from members of the community — and Democratic U.S. Senate candidate Beto O’Rourke.

The police department originally said the firing decision would be on hold until after the criminal investigation, according to The Dallas Morning News. But on Monday, the department issued a statement saying that Guyger had been fired in a hearing after an internal affairs review.

The department said Guyger “engaged in adverse conduct when she was arrested for manslaughter.” Guyger can appeal the firing.

It's unclear what exactly led to Guyger's firing — the statement does not mention the shooting itself but cites her actions when she was arrested three days later. A Dallas Police Department spokesperson declined to specify and pointed to the press release when questioned about what exactly led to Guyger's termination.

Last week, Dallas Police Chief Renee Hall said at a town hall that she couldn't yet fire Guyger in the shooting because of "local, state and federal laws," but she did not elaborate on what those were, according to WFAA-TV. The station reported that the department's general orders allow for the chief to bypass formal disciplinary procedures if she "deems it necessary to preserve the integrity of the department."

Hall also said she didn't want to compromise the criminal investigation, according to The News.

One of Jean's family attorneys wrote on Facebook on Monday that Hall told Jean's parents and their attorneys Sunday that she intended to fire Guyger. Hall said the delay was because "a premature administrative suspension could have possibly implicated Guyger's fifth amendment protections and compromised the criminal prosecution," wrote attorney Lee Merritt.

"The Jean family expressed satisfaction in this explanation and in Guyger’s termination," he wrote. "We see it as an initial victory— well received on the day Botham Jean is laid to rest in his native country in St. Lucia."

Merritt said he still is committed to seeing a conviction and appropriate sentence on a charge of murder, not manslaughter.

There is often a delay between criminal charges being filed against an officer in a police shooting and a firing. Police departments struggle to balance accountability while also giving a fair review of an officer’s actions. Often, departments will wait until after a grand jury indicts the officer before making a final employment decision.

But not always.

Former officer Roy Oliver was fired by the smaller, neighboring department of Balch Springs three days after he shot and killed 15-year-old Jordan Edwards last year. He has since been sentenced to 15 years on a murder conviction. And Dallas itself has fired officers within weeks of police shootings, though one officer who was fired was rehired after a grand jury declined to indict him.

In this case, however, Guyger's continued employment sparked protests in Dallas and became a flashpoint in the U.S. Senate race between Republican incumbent Ted Cruz and O'Rourke. O'Rourke had expressed support for firing Guyger after the shooting, while Cruz had cautioned against a rush to judgment. The two clashed over the issue in their first debate Friday in Dallas.

On Monday afternoon, Dallas Mayor Mike Rawlings issued a statement saying he agreed with the department's decision to fire Guyger.

"The swift termination of any officer who engages in misconduct that leads to the loss of innocent life is essential if the Dallas Police Department is to gain and maintain the public trust," he said.

Patrick Svitek contributed to this report.