The sniper, a sergeant in the U.K.'s elite Special Air Service (SAS), landed the astounding kill shot during a four-hour standoff with another enemy sniper.
A source told the Daily Star exactly what happened before the marksman took his fateful shot.
"It was like a game of cat-and-mouse and at one point the SAS almost gave up, believing that the terrorist had gone to ground.
"Just as the light was beginning to fade, the [ISIS] gunman moved into what he thought was a safe location and lifted his rifle up into his shoulder before the SAS shot him dead."
The British sniper with the CheyTac M200 Intervention, the same South Carolina-made rifle that holds the world record for the longest shot. It's chambered for the specialized .408 Cheyenne Tactical round, and has a range of up to 10,000 feet.
The ISIS fighter who was snuffed out by the gun was equipped with a Russian-made Dragunov rifle, and had killed and wounded several of the Brit's comrades.
The source said, "It was a classic counter-sniper operation. The ISIS gunman was moving all the time to get into the best position to get a kill. The distance was so far, that it took almost three seconds for the bullet to hit the target."
One thing's for sure: this guy deserves a medal for all-around badassery.
h/t: Daily Mail