What the hell is the story on Sullivan's Slope?!

I and my good friend were playing around on Sullivan's Slope, joking and having fun as we usually do. But after looking around the map some more, we realised that this is loaded to the brim with storytelling. We found the audio recordings and various graffiti around the place, but then we began to hear things like whispering voices, footsteps (only my friend was alive, all suspects dead), and the sound of doors opening. This caused us to look at the Sepulchre ARG and see that there might be some paranormal involvement with all of this, which is a realistic SWAT game seems out of place, but the surrealist art and weird trailers Void has put out, really makes us lean in that direction. I also remember a statue on the Hostage Rescue version of the Hotel, that would sometimes speak to you, which I have only seen video evidence of, but is creepy nonetheless.

Back to Sullivan's, we noticed that he was using lychee seeds to make a kind of poison (which is a real thing), and tested it on a bunch of animals from rats to cats, and eventually planned on doing it to humans as seen on a whiteboard in the basement. There is also weird conspiracy graffiti about the government 'always watching' with imagery of eyes everywhere. I just have no idea what on earth is going on here, and if it has a connection to the ARG. What bothers me about it all is that I have been able to piece together the story on every other map in the game, but at Sullivan's, I am so incredibly confused in the best way possible. I'm really wanting to get into the Sepulchre ARG now just to see if I can uncover anything.