[PC] [2000-2010] First person horror game hidden in low quality fps shooter

I remember watching a youtube video about this game but now cant find it, i remember it was a game that for the first two levels looked like a basic asset flip early 2000's fps, but on the third level the game would turn into this amnesia-like horror game that started out in a coastal town, but would have you going into some sort of bunker/testing facility and then into a mansion.