(You can be a mask or a human)

you walk through the corridors of the abandoned building you’ve set base in, on one of your regular perimeter checks. When you hear movement on the roof. You head up, expecting to see a mask, and you do. There’s a mask with black hair and a sniper rifle crouching on the edge of the building, clearly aiming at something. He shoots, you can’t see what he’s shooting at but you assume it’s a survivor. Then he shoots again. Did he miss? Or is there just two people? And he shoots again. And again. Until eventually he stops, and stands up. You guess he finished killing them, or they jumped off the roof or something.