What about this: everything starts normal, player is in subway train together with other passengers while train is moving. After couple minutes, the light begin to flicker until it goes out for 2 seconds before light is back on for couple minutes. During the black out, some passengers are gone. Even worse, the chair and train props where those passengers were are gone too. This event repeats every couple minutes, until it leaves player on his/her own.
You can decide the ending yourself.