A neighbor of Botham Jean who was a key witness in the murder trial of Amber Guyger has been shot dead in Dallas.

Joshua Brown, 28, was gunned down outside an apartment complex in the city's Medical District around 10.30 pm on Friday.

He was rushed to nearby Parkland Memorial Hospital, where he died from his injuries.

Witnesses say they heard several gunshots and saw a silver sedan speeding out of the apartment complex's parking lot shortly after.

Police have not apprehended or publicly identified a suspect in the fatal shooting, according to Dallas Morning News.

It's also unclear whether Brown's death was in any way connected to the Guyger's murder trial.

Brown was a neighbor of both Jean and Guyger, and his shocking slaying comes just 10 days after he broke down on the witness stand as he recounted the night Jean was fatally shot by Guyger.

Last Tuesday, Guyger was found guilty of murder, and was subsequently sentenced to 10 years in prison.

Joshua Brown, a neighbor of Botham Jean and Amber Guyger, was shot dead in Friday evening in Dallas just 10 days after delivering testimony at Guyger's murder trial

Former Dallas police officer Amber Guyger (left) was found guilty for the September 2018 murder of Botham Jean (right). Prosecutors say the 26-year-old victim was sitting in his living room, eating a bowl of vanilla ice cream when Guyger walked into his home and shot him

Following news of Brown's death, Dallas County prosecutor Jason Hermus, who led the prosecution at Guyer's trial, paid tribute to the young man for bravely agreeing to take the stand.

'He bravely came forward to testify when others wouldn't. If we had more people like him, we would have a better world,' Hermus stated.

Meanwhile, Lee Merritt, the attorney for Botham Jean's family, revealed that Brown was worried that gun violence might also end his own life.

In a Facebook post shared on Saturday, he wrote: 'Brown was still visibly shaken up from the incident when he took the stand to testify on behalf of the prosecution. His murder underscores the reality of the black experience in America.

Brown, 28, lived in the same apartment complex as Guyger and Jean

Brown was gunned down outside an apartment complex in the city's Medical District - not the complex where he lived with Guyger and Jean

A bloodstain is seen on the road outside the complex on Saturday morning

'A former athlete turned entrepreneur— Brown lived in constant fear that he could be the next victim of gun violence, either state sanctioned or otherwise. We have more work to do deal with the constant threats to our community both from within and without,' Merritt continued.

'Brown deserves the same justice he sought to ensure the Jean family. The Dallas County criminal justice system must mobilized to identify his killer and see that he is held accountable for this murder,' he added.

The timing of the Brown's death - just two days after Guyger was sentenced to 10 years in prison - has led some to speculate that it could be connected to the case.

'I just watched his testimony on Friday. I do not believe this is a coincidence,' one person wrote on Facebook.

Brown (left) points to a map of the South Side Flats housing complex, where he lived across the hall from Jean. Brown said he heard the gunshots on the night Jean was killed

Brown broke down in tears as he recounted the night Jean was killed

During his September 24 testimony, Brown, who lived across the hall from Jean at the South Side Flats housing complex, said police had knocked on both of their doors on the afternoon of the shooting about a noise complaint, even though there wasn't anything loud going on in their apartments.

The witness said he thought it might have been because both he and Jean smoked marijuana and the smell sometimes drifted into the hallway.

That night, Brown left his apartment to go watch a football game and when he came back just before 10pm he heard two gunshots and a commotion in the hallway.

He said looked through his peep hole and saw Guyger crying on the phone in the hallway and telling whoever she was speaking to that she had gone into the wrong apartment.

He said she went back into the apartment and then came out again to meet officers arriving at the scene.

Following news of Brown's death, Dallas County prosecutor Jason Hermus, who led the prosecution at Guyer's trial, paid tribute to the young man for bravely agreeing to take the stand

Brown started crying on the witness stand when he was asked about the victim. He said he'd met Jean for the first time on the day he was killed but was used to hearing the 26-year-old sing Gospel music and Drake songs in the mornings.

Judge Kemp called a recess and appeared to be choking back tears as Brown left the courtroom.

Guyger was off duty but still in uniform when she walked into Jean's home and shot him in the chest as he sat on his couch eating ice cream and watching TV.

The officer told investigators that she'd come home from a 15-hour shift and parked on the fourth floor of her apartment complex's garage - rather than the third floor where she'd been living for two months - and found the apartment's door ajar.

Believing she was at her own apartment and seeing a silhouette of a figure who didn't respond to verbal commands, Guyger said she fired two shots, killing him.

Guyger told investigators she mistakenly entered Jean's apartment, which was one floor above her own at South Side Flats (pictured), when she returned home from work at around 10pm