Hebert Conceicao Sousa was three minutes away from having to settle for a silver medal.

A single left hook now puts him in the running for the coveted Val Barker Trophy.

Brazil's Sousa waded through a sea of punches to score a dramatic, one-punch knockout of Ukraine's Oleksandr Khyzhniak to win the Gold medal in the men's middleweight division. A single left hook put Khyzhniak down on the canvas, with referee Muhammad Arisa Putra Pohan signalling an immediate end to the fight at 1:29 of round three. 

Khyzhniak—the tournament's number-one seed at middleweight—was ahead 20-18 on all five scorecards and was well on his way to securing Gold before getting clipped with a shot he never saw coming. 

The moment was shades of David Reid delivering a Gold medal for the United States in the same fashion, overcoming a massive deficit to knock out Cuba's Alfredo Duvergel in the 1996 Atlanta Olympics light middleweight final.

Sousa had to walk through hell in order to bring home just the second-ever Gold medal for Brazil. It comes five years after Robson Conceicao made history for his nation, at home in the 2016 Rio Olympics at light welterweight. 

The road to Gold for Sousa was far more difficult, having to defeat the number-two and number-one seed—in that order—to claim his hardware. Sousa advanced to the final round following a decision win over Gleb Bakshi (ROC), delivering a masterclass—if not defense-first—boxing lesson to score the upset. 

Khyzhniak didn't fall for those tricks through the first seven minutes. The two had history, with Khyzhniak having defeated Sousa in 2019 and then claiming a win via Walkover one year ago as part of a 62-fight win streak heading into Saturday's Gold medal fight. 

The free-swinging Ukrainian middleweight was throwing more than 100 punches per round, as has been the case throughout the tournament. Sousa had few answers for Khyzhniak's hard punches from all angles, including a crisp left hook and overhand right that caught the Brazilian late in round two. 

Khyzhniak was feeling the moment heading into the final round, continuing to come forward and seeking to bully Sousa. Gold was well within sight, which would have been the first for Ukraine since Vasiliy Lomachenko and Oleksandr Usyk did so in 2012 London. 

Sousa was ready to deny history. It required his standing directly in the pocket, cognizant of the incoming before connecting with a right hand and left hook. It was the hook that put Khyzhniak flat on his back, never given a chance to recover as the fight was immediately waved off while he was rising to his feet. 

The wins over the top two middleweights in the world leaves Sousa as a strong candidate for the Val Barker Trophy, awarded to the top boxer in the Olympics. 

Khyzhniak was well on his way to pleading that case for himself.  Among his wins en route to the final was a fiercely contested three-round win over Philippines' Eumir Marcial—who takes home Bronze along with Bakshi—in one of the best fight of the Olympics.

Two nights later, Khyzhniak lands on the wrong end of the most memorable moment of Tokyo 2020. 

It's one that Sousa will undoubtedly cherish forever, in addition to converting the feat into a lucrative pro contract. 

Jake Donovan is a senior writer for BoxingScene.com. Twitter: @JakeNDaBox