Transcript for 911 call from off-duty officer after she fatally shot a man in his own apartment
The breaking headline out of Dallas at this hour. Police call it a very unique Involving an off-duty officer who shot and killed her neighbor in his own apartment. Reporter: Amber guyger was an off-duty police officer, arriving home from work. Her neighbor, botham Jean was in his apartment. What we knew is she went to his she thought it was hers. When she saw him, she fatally shot him. The aftermath of that incident caught in this video. Now for the first time, we're hearing officer guyger's 911 call. I shot a guy, thinking he was in my apartment. Reporter: An attorney for Jean's family listening with us. The audio obtained exclusively by Dallas station WFAA. All I can imagine is botham on the ground taking his last breath. And that was very difficult for me. Okay. We have help on the way. I know, but I'm going to lose my job. I thought it was my apartment. Reporter: In the recording, guyger can be heard growing increasingly distraught. 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. Hey, bud. Reporter: Guyger now potentially facing prison time. Jean's family left in anguish. She took my life away. Like my very own life. Reporter: While the community grapples with unanswered questions. We're still dealing with an America where black people are killed in some of the most arbitrary ways. Driving while black, walking while black, and now we have to add living while black. Reporter: Sparking protests over what some say is a lack of transparency coming from the Dallas police department in the wake of the shooting. Now that 911 call beginning to shed light on what happened that night. Botham Jean described as a ray of sunshine. Botham had a love for everything and everyone. So I just want the message of love to permeate throughout this whole process. Reporter: An active member of the church of Christ. The spirit of the lord let it rise Reporter: He was beloved by many. This packed service in his honor shows. This person has been on patrol for four years. They have a pretty good idea of how to handle stressful situations at that point. Reporter: There is nothing to say the two neighbors had a relationship. But on September 6th. After a more than 13-hour shift, guyger, who was off duty arrived back to her apartment building where her and Jean's lives would cross in the worst way imaginable. She could be running from job to job. That factors in here. Reporter: Guyger lived on the third floor parked on the fourth floor that night. She headed to the apartment directly above her unit, thinking, she said, it was her own. The door, she says, was slightly the interior dark. I thought it was my apartment. She says that over and over again in this five-minute recording. Is that significant to you? It's significant to the point that it makes me feel that that call was staged. It makes me feel that she has already spoken with someone. Reporter: Guyger still in uniform says she thought she spotted a burglar. She fired two shots, hit being him in the chest. 20 times she tells the dispatcher she thought the apartment was her own, at one point saying she was tired. No, no. I, . I'm tired. The thing that stands out the very most to me was the fact that when I listen to that call, not one time did I hear amber guyger say she was in fear of her life. Reporter: The Dallas police department was quick to respond, turning the case over to the state investigator, the Texas rangers. In order for us to be completely transparent to this community based on the circumstances we have invited the Texas rangers to conduct this investigation. Reporter: But it would be a few days before guyger was identified and arrested for man slaughter. The family have many questions for the authorities. The main one being that this police officer should not be given any preferential treatment. Reporter: As details of that night emerge, protests grew louder, many demanding justice for Jean. This is a case that raises a lot of sensitive questions. And there's going to be enormous public interest. And consequently, there's more of a desire to get that evidence out faster. Reporter: A woman who says she lived in the building and shot this video in the moments after the incident questioned the validity of the officer's The elevator, garage, hallways, everything is marked with what floor you are on. So she would have passed plenty of indications to let her know she was on the fourth floor. Reporter: At the same time, the Jean family told ABC they questioned the statements made in the affidavit. Independent witnesses have already come forward to say they heard the officer pounding on the door. Reporter: A grand jury indicted guyger. It's possible the grand jury decided on its own, more likely that the prosecutors played a role in moving this from manslaughter to murder. Reporter: Geiger's attorney spoke to the affiliate station last November. Her actions are justified under the law. So you don't prosecute people that, one, make a mistake, that don't have a criminal intent to commit a crime. Reporter: Today both parties are under a gag order, barring them from discussing the criminal case. Jean's family has also filed a civil lawsuit against the city of Dallas and guyger. I thought it was my apartment. Oh, my god. Reporter: The chilling audio offers clarity about that night but still leaves many questions. Only two know the full answer. But one is silenced forever. I just want to let people know that botham loved, he didn't even have to know you, he just loved everybody. Reporter: For "Nightline," I'm Marcus Moore in Dallas, The trial in this case is expected to start in September.
This transcript has been automatically generated and may not be 100% accurate.