San Bernardino police said the shooting happened around 9 p.m. Friday in the area of Chestnut Street and Rancho Avenue.
Victim Anthony Hernandez, 46, was walking with his girlfriend when a man got out of his car and approached the couple.
Both men got into a brief physical fight and during the altercation, the suspect pulled out a handgun and fired a shot.
Hernandez was struck once and died, police said.
Witnesses and evidence at the scene indicate the suspect was in a white vehicle that was being driven by a woman with blonde hair, according to investigators. Both fled the scene after the shooting.
Anyone with information about the case was asked to contact Detective Sawyer at (909) 384-5630 or Sgt. Kokesh at (909) 384-5613.