Brown, a key witness in the trial, lived across the hall from Botham Jean at Dallas' South Side Flats apartments last year when officer Amber Guyger walked into Jean's apartment, mistaking it for her own, and killed Jean.
Brown was killed Friday at his current home, the Atera Apartments, about five miles from his former complex where he, Guyger and Jean all lived.
Before his own death, Brown lived in constant fear of gun violence, said Lee Merritt, an attorney for Brown's family.
Authorities have not said whether there's any connection between Brown's death and his testimony in Guyger's trial, which ended last week.
Brown had been shot before
Brown had survived a shooting nearly a year before his death, Merritt said.
He was shot near a strip club in Dallas in November 2018, Merritt said. Nicholas Shaquan Diggs was killed in the shooting, Merritt told CNN by phone Sunday.
Both Brown and his family believed he was targeted in that shooting by someone he knew and had grown up with.
"And he was concerned that that person might try to come back and finish the job," Merritt said, adding that the shooter in that case hasn't been caught.
Brown moved out of South Side Flats about three months after Jean was killed in September 2018, according to Merritt. He tried to keep a "low profile intentionally until some of the heat from the shooting in November passed over," Merritt added.
He was subpoenaed to testify
Yet, he was thrust into the spotlight of a major trial.
"He did not want to testify in that trial," Merritt said. "He made it clear he had no interest in testifying in open court in that trial."
Despite his protestations, Brown was subpoenaed to testify, according to Merritt, who is also an attorney for Jean's family.
The attention that came with being a part of a high-profile trial didn't sit well with Brown, who was bothered by the attention, Merritt said.
"(Brown's mother) knows that her son was really bothered by the fact that he was given a lot of exposure from the trial, a lot of unwanted attention," he said.
Although Merritt said the family wasn't aware of specific threats against Brown for testifying, they did know about comments online calling him a "snitch" and saying he was cooperating with the state.
The Dallas Police Department hasn't identified a suspect publicly in Brown's death and does not yet have a motive, according to a statement released Sunday by police chief Renee Hall.
Witnesses told police they saw a silver, four-door sedan leaving the parking lot at a high rate of speed following the shooting and police have asked the public to come forward with information on the case.
Mayor Eric Johnson said in a tweet Sunday that the department would "conduct a thorough investigation into the death of Joshua Brown," and urged people to not speculate about the case before the investigation is completed.
Other officials shared his sentiment Sunday. Dallas County Judge Clay Jenkins, who is not a court judge, but is head of the county commissioners said in a tweet Saturday that he shared "the community's profound sense of shock and anger over this evil murder." He said the county and city would "work to ensure a transparent and thorough investigation," adding that career professionals were hard at work on the case and should be extended "grace."