Not to add to your creepy thoughts but could it be the building manager? A friend living in New York one summer while on a working visa had that happen to her and only her friend came to pick her up and saw the guy on his hands and knees looking in she would not have known because he drilled through the wall from the bathroom under her sink to the hall when he supposedly came to repair something in the bathroom for her she was so weirded out even wiht a month and half to go she phoned home to get her parents to organise tickets home for her. turned out he had numerous convictions for sexual assault and was not flagged because he used his middle name when applying for the job!!!!