Originally released in March 2001, the game was available for the Game Boy Advance and was created as an intereactive story. You can choose to follow Cybil or Harry and the player is given various choices to progress through the game and are rewarded with digital trading cards at the end.
Fortunately for Silent Hill fans Giromancy of the Silent Hill Community has ported Harry Mason's story over to PC with Cybil on the way in the near future. The ported game even features alternative endings.
You can download the game to play yourself right here.