INJURED PERSON:
I used to live a good life until I got injured some days ago. On that day I felt free in the sky, I went towards that building on the hill. It was a massive thing, shiny as hell; I heard rumors of killer monsters in it but I payed no heed. I was gliding towards an open area, then I was stuck by something and I fell. While falling I saw nothing where I was hit. I cracked my skull and broke my wing, but I suppose that I was lucky. That invisible killer caused the deaths of many of my kind, and I hear that they are just about everywhere.

What is the killer