When firing a weapon or throwing something, the game targets the square you last targeted (or examined?) relative to your location, rather than the nearest enemy or yourself. So you I try to throw a rock at a boomer and before I realize where the reticle is, I end up quarterbacking it 32 squares in the opposite direction and smashing out the headlight on my car, so I can’t see anymore.
This only seems to happen if you pressed Enter on that square, but I have no idea what the exact criteria is.