Lies and Betrayal

I left the room and P.A. was awaiting me. I asked him about his history he said it wasn't important. I told him a bit about the conversation with Brian excluding the last bit and he told me. This confirms it. He's the experiment. I was brought into The Empty City to deal with him. Great. How am I supposed to do this. I can't just kill him. He seems to be able to know where I am at all times. If I make a single threatening motion towards him he'll notice. Think Faceless think...