Jurors saw disturbing police video Tuesday of the moments after an off-duty Dallas officer fatally shot an unarmed neighbor last year after she said she mistook his apartment for her own. Former officer Amber Guyger, who is standing trial for murder, is seen on the video ushering officers from a hallway into the apartment where Botham Jean lay mortally wounded.

Prosecutors said during opening statements Monday that Jean was sitting in his living room eating a bowl of vanilla ice cream when Guyger walked into his home and shot him.

"I thought it was my apartment," Guyger is seen saying on the video, recorded on the body camera of one of the officers responding to her 911 call September 6, 2018.

Get Breaking News Delivered to Your Inbox

Guyger appears frantic in the video. When the officers ask her where Jean is shot, she responds, "Top left, top left."

One of the officers begins CPR and chest compressions on Jean, who is seen lying on the floor, motionless and covered in blood. Paramedics arrive about five minutes later.

WARNING: Disturbing video

Jurors also on Tuesday heard a recording of Guyger's 911 call. An emergency worker who took the call testified Tuesday that Guyger placed it just before 10 p.m. and requested an ambulance.

The recording of the 911 call was previously obtained by a Dallas TV station. In the call, Guyger says "I thought it was my apartment" nearly 20 times. She also says: "I'm gonna lose my job" and "I am going to need a supervisor."

Former Dallas police officer Amber Guyger, center, arrives for the first day of her murder trial in a Dallas courtroom, Monday, Sept. 23, 2019. Guyger is accused of shooting her black neighbor in his Dallas apartment. Tom Fox/The Dallas Morning News via AP, Pool

Guyger was returning to the apartment complex where she lived in an apartment on a different floor from Jean after working a 13-and-a-half-hour shift, a prosecutor said Monday. She was off-duty but still in uniform when the shooting happened.

She told investigators that she parked on the fourth floor of her apartment complex's garage — rather than the third floor, where she lived — and found the apartment's door ajar. Her defense is arguing that she thought Jean was a burglar in her own home and that Jean was coming towards her when she opened fire.

The 911 call and video may provide key pieces of evidence because the prosecution and defense have laid out differing accounts of how Guyger reacted after the shooting. Dallas County prosecutor Jason Hermus said in opening statements that Guyger on the 911 call appeared "as concerned or more concerned about how this is going to concern her than this poor guy on the floor next to her."

Amber Guyger, right, and Botham Jean. AP

Hermus said Guyger never said on the 911 call that Jean was approaching her or threatening her when she opened fire. He contends that Guyger, instead of helping Jean, went out into the hallway in the final moments of his life. He also said she texted her Dallas police partner, with whom she was romantically involved.

But defense attorney Robert Rogers said Guyger was horrified once she realized her mistake. Rogers said she immediately called for EMS and only left the apartment to show responding officers where it was located. On the video, Guyger is heard saying "He's in here."

Tuesday, several officers who responded to the scene took to the stand, along with neighbors who heard the gunshots. Jean's neighbor, Joshua Brown, said he heading back to his apartment when he heard what sounded like two people "meeting by surprise" followed by two shots.

He said he didn't hear anyone shouting police commands, such as "show me your hands," but on defense cross-examination said he couldn't make out what the two people were saying.

The trial jury will decide whether the 31-year-old committed murder, a lesser offense such as manslaughter or criminally negligent homicide or no crime at all. The outcome may hang on whether the jury believes that Guyger's mistake was reasonable, according to legal experts.