You're the Doorman!

After many confusing and stressful nights of having to deal with Dopplegangers, you feel like quitting. you sigh and sit down on your chair, waiting for the next batch of people. after calling the D.D.D (Doppelganger Detection Department) many times, and having to repeat the number (3312) a lot, you start getting annoyed with everything. you check the date, it reads "February 10th, 1955.". You sigh, glancing at the huge window in the room, until... someone comes in. The MilkMan stands at the window, dropping in his I.D and request form. he looks tired as you check it. It seems normal, his name was Francis Mosses on the 3rd floor, room 2, he lived by himself. you debated on letting him in, but the red stuff covering his body got you intrigued, wondering if he was a doppleganger. you ask him what the red stuff was

Milkman: ... Its Scarlet milk. a new kind of milk..