Hathcock's 2500 Yard Shot...Here's the skinny that I got from somebody who claimed to have been on-site.
The weapon was sandbagged in and preregistered on a designated spot...not to engage individual enemy personnel...but to damage vehicles. When a vehicle passed a designated point, observed by the spotter, the signal was given to fire, so that the bullet and the vehicle would meet at the target area. Sorta like the old VASCAR speed traps. Line to line distance, and calculated speed.
A spotter noticed movement, and determined that it was an enemy soldier, scanning the area with field glasses...and guessed to be a forward observer attempting to figure out where the fire was coming from that was damaging their trucks...and a bet was struck. He moved close to the designated impact point.
It was noted that within a second or two after the shot fired, that the soldier...kneeling at the time of the shot...stood up and was struck high on the chest. It was reckoned that if he hadn't stood up, the shot would have gone over his head.
Anyway...That's the story I got. Dunno how true, but it sounds plausible.
I'd place it in the same category as Billy Dixon's 7/8ths mile hit on a Kiowa warrior with a .50 caliber Sharps rifle. About 99.5% luck.