The Dallas man who was murdered shortly after providing key testimony in the trial against killer cop Amber Guyger was set to take the stand in a civil lawsuit against the police department, according to a report.

Joshua Brown, 28, who was victim Botham Jean’s neighbor, was shot to death Friday night in an ambush outside his apartment in a Dallas neighborhood, according to police. No suspects have been arrested in the slaying.

“To have a key witness suddenly be killed is suspicious. Was this related to the trial? There is no clear indication,” attorney Lee Merritt, who represents the Jean family, told CBS News.

Brown’s death came days after Guyger was convicted of fatally shooting 26-year-old Jean, who she believed was an intruder when she mistakenly entered his apartment instead of her own.

Merritt said Brown would have been one of their first witnesses in the Jean family’s wrongful-death suit against the city of Dallas, which claims Dallas police failed to adequately train Guyger, according to CBS News.

Brown testified at Guyger’s trial about the September 2018 night that Jean was shot dead in his own apartment. He said he heard what sounded like “two people meeting by surprise” while he was in a hallway on the floor where he and Jean lived.

He also rejected Guyger’s claims during the trial that she used commands such as “put your hands up” before shooting Jean.

“She didn’t. No one heard that. No neighbors. No passerby’s [sic]. Not Joshua as he walked down the corridor. No one,” Merritt wrote on Facebook.

Merritt has called for answers in the death of Brown, who he said lived in “constant fear that he could be the next victim of gun violence.”

Brown — a roofing contractor and Airbnb host — had previously survived a shooting in November 2018 outside of a Dallas strip club, CNN reported. His family believed he had been targeted in the shooting by someone from his childhood.

The suspect was never nabbed and Brown “was concerned that person might try and come back and finish the job,” according to Merritt.

It led him to move out of the same apartment complex where he had once lived on the same floor as Jean.

Brown had been trying to keep a “low profile intentionally until some of the heat from the shooting in November passed over,” Merritt said.

His fear made him hesitant to take the stand in the trial against Guyger.

“He was reluctant to testify in this case because he had been shot at and he thought some people might want to do harm to him,” Merritt told CBS.

Though Brown’s family wasn’t aware of any threats against him over his testimony, Meritt said that authorities could have offered him protection.

“If he had concerns for his safety, then the city, the county had an obligation to ensure that those concerns were met,” Meritt told the news outlet.

The lawyer did not respond to a Post request for comment.

With Post wires