sniper

A sniper is a military/paramilitary marksman who engages targets from positions of concealment or at distances exceeding the target's detection capabilities. Snipers generally have specialized training and are equipped with high-precision rifles and high-magnification optics, and often also serve as scouts/observers feeding tactical information back to their units or command headquarters.
In addition to long-range and high-grade marksmanship, military snipers are trained in a variety of special operation techniques: detection, stalking, target range estimation methods, camouflage, field craft, infiltration, special reconnaissance and observation, surveillance and target acquisition.

View More On Wikipedia.org