I believe the speaker in the song is Sam indefinitely. In the game, Sam seems to have a way messing with everybody's mind. The listener is most likely Gersh but could possibly be Richtofen considering he locked her in the room with fluffy and both Gersh and Richtofen did something terrible that they will regret forever. Gersh was definitely driven insane by Sam. Richtofen could be having second thoughts about creating the zombies. This and Sam could be driving him to crazyness. I think Richtofen will end up killing everybody in the world trying to end the zombies due to his insanity. This could explain Der Riese. Richtofen was trying to end it at the source but was foiled when the teleporter malfunctioned. This kindof an "off-the-wall" theory but it might explain somethings to people.