Bryan Forbes is an undercover agent for the FBI according to the Vice City Stories official website (In the mission "Snapshot Longshot" his ID Card states he is a DEA Agent). He is just a new employer for Victor and Lance when he provides missions for them, and aids Victor on his rise in power in Vice City. His white suit and pink shirt resemble those of Sonny Crockett from the 1980s Miami Vice television series. His suit also shares the same color with Lance's outfit in Vice City.
Lance soon finds out that he is an undercover cop, both him and Victor capture him and take him to an abandoned building where they tie him up and get some info from him. He is killed by Victor when he tries to escape after duping Lance and Victor into entering a gay white supremacist bar, Lance did not have any intention of killing him because he did not yet reveal where a big cocaine shipment was, however Lance learns that Martinez will be receiving the shipment.
The official Vice City Stories website features a news report with pictures of a man in the same suit with his face blurred. The news report mentions "Agent BF," leading some to believe that the man in the picture is indeed Bryan Forbes.