Joshua Brown, who was killed Friday night in Dallas, was a key witness in the murder trial of former police officer Amber Guyger because he was able to provide testimony about events the night his neighbor, Botham Jean, was fatally shot in his apartment.

Dallas police were still looking Sunday for a suspect and a motive in Brown's shooting and have released few details about his death.

Brown, 28, lived across the hall from Jean, 26, at the Southside Flats apartment building in Dallas, where Guyger fatally shot Jean last year when she mistakenly entered his apartment instead of her own.

In a closely watched trial, Guyger, 31, was found guilty of murder Tuesday and sentenced to 10 years in prison. Brown helped the prosecution piece together the events of Jean’s murder that ultimately led to Guyger’s conviction.

Brown was found lying on the ground in the parking lot of an apartment complex Friday night with multiple gunshot wounds to his lower body, police said. He was taken to a hospital, where he died from his injuries. Police said witnesses reported seeing a sedan leaving the apartment complex at a high speed.

Brown, born in Jacksonville, Florida, was shot only a few miles from where he lived when Jean was murdered.

He testified that on his way home from watching a football game on the day Jean was killed, he heard an exchange between two people who both seemed “surprised” while in the hallway of his building.

“Right after” the exchange, he said, he heard two quick gun shots.

When asked by prosecutors if he could make out what words Guyger and Jean exchanged, Brown said no. When questioned, he said he did not hear any police commands from Guyger such as “put your hands up.”

He said on the witness stand that he initially ran away when he heard Guyger’s gun fired, and made his way back to his apartment a few minutes later.

Once in his apartment, Brown said, he could see Guyger crying and walking back and forth in the hallway. She was on the phone, explaining she had entered the wrong apartment. Brown also testified that he saw Guyger reenter Jean’s apartment.

Brown said he and Jean met for the first time the day Jean was murdered, when they received a noise complaint.

Often emotional during his testimony, Brown was asked more than once to speak louder and cried on the witness stand.

People on social media pointed out that Brown testified in a Dragon Ball Z T-shirt, believing him to be a fan of the Japanese anime TV show. Brown said in court that he managed Airbnbs for a living, had previously worked as a roofer and had graduated from college in Florida with a degree in science.

One of many notable parts of Brown’s testimony came when he said he had also walked to the wrong floor in his apartment building before, which was Guyger’s explanation for why she entered Jean’s apartment, thinking it was her own.

Brown said that on one occasion, he even put his key in the door of an apartment on the wrong floor. Yet, he noted, there was a large vase on the third level where Guyger lived that made him realize he was not on the fourth level, where he and Jean lived across from one another.

In an interview with "Today," a lawyer who represented Jean's family and is now working with Brown’s relatives, said Sunday that Brown’s role in the trial caused him to fear “for his life.”

The lawyer, S. Lee Merritt, attributed that fear, in part, to a shooting that occurred in recent months during a birthday party at a Dallas club that Brown attended. Brown was shot in the foot, Merritt said, and a friend of his was killed.

It wasn’t clear what caused the incident, but Merritt said Brown knew the shooter and worried the person “might come back to try and finish the job.”

Brown’s relatives told Merritt that he worried about how the trial’s publicity could leave him more exposed to "people who wished him harm," and how he could be viewed as a “snitch” for cooperating with law enforcement in Guyger’s prosecution.

Brown heard such pushback in the days after the trial, Merritt said.

Merritt said he had no evidence to suggest Brown’s death was in retaliation for his testimony, but he added, “it is certainly worth investigating or looking into and we expect the city of Dallas to apply all of its resources and manpower to figure out what happened."