Image copyright Reuters Image caption Joshua Brown at the trial of Amber Guyger

A witness who testified at the "wrong flat" murder trial of a US policewoman has been shot dead outside his home, just days after she was sentenced.

Joshua Brown had lived on the same floor of a Texas building as victim Botham Jean, shot by Amber Guyger after she apparently mistook his flat for her own and him for an intruder.

Mr Brown had wept as he delivered his testimony about the killing in court.

He died on Friday night in an apparent drive-by shooting in Dallas.

As police officers investigated, there was no suggestion that his death was linked to the Guyger trial. There are still no suspects in the killing, police chief U Renee Hall said on Sunday.

Lee Merritt, a lawyer for Botham Jean's family, called for the US justice system to find and hold to account the killer of Mr Brown who, like Jean, had been a black man.

"Brown deserves the same justice he sought to ensure the Jean family," Mr Merritt said in a statement.

Dallas Mayor Eric Johnson asked the public to "refrain from speculation" as the investigation continues.

Skip Twitter post by @DallasMayor I trust the Dallas Police Department will conduct a thorough investigation into the death of Joshua Brown. Until we know more about this incident, I encourage everyone to refrain from speculation. (1/2) — Office of Mayor Eric Johnson (@DallasMayor) October 6, 2019 Report

How did Brown die?

Shortly after 22:30 (03:00 GMT Saturday), police responded to a shooting in an apartment block different from the one where Jean had been killed in September 2018.

Witnesses flagged down the police officers and directed them to a parking lot where Mr Brown was lying on the ground with multiple gunshot injuries.

He was taken to a hospital where he died.

The witnesses told police they had heard several shots and had seen a silver four-door sedan speeding out of the parking lot.

Who was Joshua Brown?

The 28-year-old was described by US media as a former athlete and entrepreneur.

He testified at Guyger's trial that, on 6 September of last year, he had been in a hallway on the fourth floor where he and Jean lived when he heard sounds from Jean's apartment.

These he described as the sound of "two people meeting by surprise" followed by two gunshots.

Media playback is unsupported on your device Media caption Brandt Jean embraces his brother's killer in court

As he bore witness in court, he began weeping and wiped tears from his eyes with his T-shirt.

Amber Guyger was sentenced to 10 years in prison on Wednesday.

Dallas County prosecutor Jason Hermus paid tribute to Mr Brown, saying he "bravely came forward to testify when others wouldn't".

"If we had more people like him, we would have a better world," he added.