Carlos Hathcock was a U.S. Marine Corps sniper who had racked up a high enough kill count during his two tours in the Vietnam War to earn a bounty on his head for $30,000 from the North Vietnamese government.
Inspired by the bounty, an unknown Vietnamese sniper set out to try and kill Hathcock, unaware that to do so would be like trying to sneak up on Batman and slap him in the penis.
Hathcock was drawn out of camp when the enemy sniper shot several of his fellow Marines, despite knowing that the man was simply trying to bait him. So it was sort of like Enemy at the Gates, only with fewer fake German accents. To avoid a hasty debraining via high-velocity bullet, Hathcock would have to move slowly and stay out of sight, so he crawled the distance between himself and the other sniper on his stomach, making sure to keep the sun behind him.
He kept going like this until he thought he saw a glint of light, like when the sun is reflected off a piece of glass during a boss battle in Metal Gear Solid 3.
The experienced Hathcock fired at the glimmer, knowing it to be either his foe or a tiny mirror placed out in the jungle for no conceivable reason. As it turns out, it was the former, and Hathcock's bullet passed clean through the enemy sniper's scope from 500 yards away, threading the needle at close to one-third of a mile.
Bear in mind that the typical rifle scope is only a couple of inches wide at the very most, so Hathcock had to place his shot perfectly for the bullet to pass through it and not hit the sides of the device. Also, the enemy sniper had to have been facing him, with his gun more or less leveled directly toward Hathcock's position. So, in the span of the half-second he had to spare before his foe spotted him and erased him from time, Hathcock fired a round through a 2-inch circle he wasn't even positive was there, draped in dense jungle about three city blocks away.