A key witness in the murder trial of a former Dallas police officer is now dead. Joshua Brown, Botham Jean’s neighbor, was shot to death on Friday. His testimony helped prosecutors piece together the events of Jean’s murder, and ultimately led to Amber Guyger’s conviction.

Dallas police say they are investigating Friday night’s shooting and, so far, do not have any suspects or a motive. The attorney for Botham Jean’s family is also the attorney for Brown and says he should have been protected after he testified at Guyger’s murder trial. The Jean family has filed a civil case against the city of Dallas for the murder of their son Botham. Merritt says Brown would have been one of their first witnesses.   On the witness stand, Brown recalled feeling startled when he heard the gunshots that would ultimately take Botham Jean’s life. Now the Jean family and their attorney Lee Merritt are demanding answers.

“To have a key witness, suddenly be killed is suspicious. Was this related to the trial? There is no clear indication,” Merritt told CBS News’ Omar Villafranca. Brown took the stand in Guyger’s trial and gave emotional testimony about the night Jean was killed last September. Brown said he was in a hallway when he heard the two gunshots. The shooting that killed Brown happened at a different apartment complex than the one where Guyger and Jean lived. Witnesses described hearing several gunshots Friday night, and seeing a silver four-door sedan speeding away from the parking lot. Merritt says Brown was scared someone was after him, after he was involved in a separate shooting incident in Dallas.

“He had been shot less than a year ago and someone standing near him was killed,” Merritt said. “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.”

Asked if the police could have offered Brown protection, Merritt said, “if he had concerns for his safety, then the city, the county had an obligation to ensure that those concerns were met.”

Brown was working in roofing and property management.

More about: