Brian Bradley was Kyle's former partner and friend in the Nintendo DS video game, Hotel Dusk: Room 215. Three years ago, he switched sides and gave confidential police information to a Manhattan based crime syndicate he was supposed to be investigating. Kyle shot him, but Bradley disappeared and hasn't been seen since.
Working alongside Kyle in the N.Y.P.D, Bradley was assigned as an undercover cop in the Nile case where the crime syndicate Nile were stealing art. Soon Bradley was approached by Nile operative "Norman" A.K.A Robert Evans who informed him that Nile had taken Bradley's kid sister Mila and unless he disclosed secret police information to the crime syndicate, Mila would be killed. During this time working as a forced informant for Nile, Bradley discovered the secrets behind Nile itself including Dunning Smith being the "Phantom Painter" Osterzone and that Dunning's daughter was kidnapped by Nile too.
As his work continued he came across "Angel Opening A Door", the masterpiece of Osterzone. Feeling Dunning's pain of having a loved one kidnapped, Bradley takes the painting and a case of money after shooting one of his associates. The associate was Danny, best friend to Louis DeNonno who was connected to Kyle Hyde. Before long, Bradley was able to see his sister again. However he was too late; Mila was dead by the hands of Robert Evans. Attempting to convince Bradley to work for him, Evans was able to bring Bradley back aboard. Despite his choice, Bradley had only one goal in mind -- kill Robert Evans.
Around this time, Hyde found out about Bradley's treachery and confronted him on the New York docks. A furious Hyde shot Bradley and he fell into the Hudson river. Surviving, Bradley continued to hunt Evans. 6 months before the main game story, Bradley turns up at Robbins Memorial Hospital where Mila Evans (Daughter of Robert Evans) was still in a coma. Seeing his kid sister in Mila, he felt so nostalgic and gave her the bracelet he was wearing; the bracelet which used to belong to his sister.
Soon after, Bradley arrived at Hotel Dusk. That night, he had a few drinks with Dunning Smith and starts talking to him about Nile, about Evans, about everything. Dunning pretended not to know anything but Bradley kept talking. Before leaving, Bradley left the "Angel Opening A Door" painting in room 217 of Hotel Dusk, the same room he had been staying in. Along with that, he left clues for his old partner Hyde to pick up on including signing into the hotel using Kyle's own name. It is heavily implied that around this time, Bradley succeeded in hunting down and killing Evans.
After finishing what he set out to do, Bradley was on the run from Nile as well as the police. Leaving behind a handwritten note for Kyle to find, he told his ex-partner to give up chasing him because there was no point in chasing a "ghost". His fate is unknown.