(CNN) The former Dallas police officer facing a murder charge in the shooting of Botham Jean made a desperate 911 call in which she says at least 19 times that she thought she was in her own apartment.

Amber Guyger, 30, alternates between talking to the dispatcher, to Jean, to herself, and finally, to responding officers.

Crying as the dispatcher tells her help is on the way, she replies, "I know, but I'm going to lose my job. I thought it was my apartment."

To Jean, she says, "Hey man," before saying to no one in particular, "F**k."

She was correct about her job. After the Texas Rangers, taking the lead in the investigation, charged Guyger with manslaughter, the Dallas Police Department fired the four-year veteran during a September 24 hearing.

Initially charged with manslaughter and released from Kaufman County Jail on $300,000 bail, a grand jury in November upgraded the charge to murder. Her attorney has said the shooting was a "true mistake" and that a jury will acquit her.

'Stay with me, bud'

The September 6 call, obtained and made public by Dallas news station WFAA , begins just before 10 p.m. Guyger requests police and paramedics and says she walked into an apartment thinking it was hers, and "shot a guy."

"You shot someone?" the dispatcher replies.

"Yes, I thought it was my apartment. I'm f**ked. Oh my God. I'm sorry," Guyger says.

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"I'm inside the apartment with him," she tells the dispatcher, before urging Jean, "Hey, come on, man."

She continues, "Hey, bud. Hey, bud. Hey, bud. Come on. Oh, f**k. ... I thought it was my apartment."

Guyger urges the dispatcher to hurry before repeating several times that she thought she was in her own apartment. "I could've sworn I parked on the third floor," she says.

As the dispatcher asks for the gate code and assures Guyger police are en route, Guyger is still talking to Jean: "Hey, bud. Hey, bud. They're coming. They're coming. I'm sorry, man."

Asked where Jean was shot, Guyger replies, "He's on the top left."

"Oh my God. I'm done. I didn't mean to. I didn't mean to. I didn't mean to. I'm so sorry," Guyger continues, telling Jean, "Stay with me, bud."

The dispatcher tells Guyger police are almost there. Guyger continues to curse as the realization of what she's done continues to set in.

"I thought it was my apartment. I thought it was my apartment. Holy f**k. I thought it was my apartment. Oh my God. F**k. I thought it was my apartment. I'm so sorry. I'm so sorry. F**k."

Botham Jean, 26, was killed in his own apartment last year, police say.

She questions herself: "I... I ... How the f**k did I put the... How did I... How did I... I'm so tired. Hurry."

As police arrive, she calls to them and says, "No, it's me. I'm off duty. I'm off duty. I f**ked ... I thought they were in my apartment. I thought this was my floor."

The call ends. Jean, who was 26 and unarmed, died later at a hospital.

Attorney: Guyger guilty of a 'true mistake'

The door was slightly ajar as she tried to use her key, which has an electronic chip. When she opened the door, she saw the interior was almost completely dark, according to the affidavit. She described seeing a large silhouette and, believing there was an intruder in her apartment, drew her firearm.

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She issued verbal commands, but Jean, being in his own home, did not heed them, and Guyger fired two shots, hitting him once in the torso, the affidavit said.

Guyger called 911 and began administering first aid to Jean. She turned on the lights while on the phone with 911. Only when asked for her address did she realize she was in the wrong apartment, she told police.

The killing sparked days of protest , and angry demonstrators demanded justice. Protesters interrupted a City Council meeting to demand accountability and police reform.

When then-Dallas County District Attorney Faith Johnson presented the manslaughter case to a grand jury, jurors upgraded the charge to murder, which Johnson explained meant that they felt Guyger's actions were "knowing" or intentional.

A judge permitted Guyger to remain free on her original bail.

"This is a terrible tragedy that resulted from a true mistake," Robert Rogers, Guyger's attorney, said at the time. "We are confident that a dispassionate jury in a fair forum will objectively apply the law to the facts and find Amber not guilty."

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Jean's mother, Allison Jean, applauded the upgraded charge, saying that Guyger "inflicted tremendous evil on my son."

"He didn't deserve it," she said. "He was seated in his own apartment. He felt safe and he was violated by her coming in and murdering him."

Allison Jean said she hopes a guilty verdict and suitable punishment will spur Guyger to reflect on what she has done and the pain she has caused.

Jean's parents filed a federal lawsuit against Guyger and the city in October, alleging Guyger used excessive force. The ex-police officer's trial is slated to begin in September.