(Reuters) - A former Dallas police officer was charged with murder on Friday for shooting an unarmed black neighbor whose apartment she said she mistakenly entered instead of her own, prosecutors said.

Officer Amber Guyger appears in a booking photo provided by the Kaufman County Sheriff's Office, September 10, 2018. Kaufman County Sheriff's Office/Handout via REUTERS

Amber Guyger, 30, surrendered to authorities after a grand jury indicted her on a charge of murder in the Sept. 6 death of Botham Jean, 26, Dallas County District Attorney’s spokeswoman Kimberlee Leach said by phone.

Guyger, who lived in an apartment one floor below Jean’s unit, told investigators she mistook Jean for an intruder after she entered his apartment by mistake and he appeared in the darkness, police said.

Guyger walked into the apartment after returning from a work shift and was able to enter because Jean’s door was slightly ajar, according to a Texas law enforcement account of the incident.

The killing of an unarmed black man by a white officer in uniform sparked demonstrations in the Texas city, with protesters calling for Guyger, a four-year veteran of the Dallas police force, to be charged with murder.

The shooting followed several years of scrutiny of law enforcement in the United States over questions of racial bias.

An attorney for Guyger did not immediately return a call seeking comment.

“We have taken the position from day one that we want to make sure that justice is done for everybody and it’s equal justice, it’s not one-sided or it’s not blinded,” Dallas County District Attorney Faith Johnson, whose prosecutors presented evidence to the grand jury, said at a news conference.

Guyger was arrested in September for shooting Jean and initially charged with manslaughter, a lesser offense for an unlawful killing that does not involve malice aforethought. She was released after posting bond of $300,000.

The bond was re-instated after she was charged with murder, Leach said.

Within days of the manslaughter charge, Johnson pledged to convene a grand jury to more fully examine the shooting.

Jean’s mother, Allison Jean, spoke at the news conference on Friday alongside the district attorney.

“I look forward to the next step, which is a conviction of murder of Amber Guyger and also of a penalty, the proper penalty, that will cause her to reflect on what she has done,” Allison Jean said.

Guyger was at first placed on administrative leave after shooting Jean but was fired days later, with the Dallas police chief citing her actions the night of the shooting and afterward.