Once you fire your first shot, you've marked your location. And because of the way the system works, all bullet paths are shown with a red line; the snipers' advantage is, for that first shot, there is no line.

I can usually fire off two shots before my opponent can get their bearings, but it's hard to keep it up once they know where you are. After that point, there's really no reason to stick around if you can help it.