It was one of the most stunning finishes in championship-boxing history.
Manny Pacquiao had appeared to shake off the impact of a hard, third-round knockdown he suffered against Juan Manuel Marquez. He had knocked down Marquez in the fifth round, and he had hurt his rival with crisp, clean shots.
The sixth round was Pacquiao's...until Marquez delivered a devastating knockout punch in the final seconds of the round.
Pacquiao fell to the canvas as if he were a bull moose who had been gored by his rival. Pacquiao was unconscious before he hit the ground.
He was out for at least two minutes before his handlers were able to get him to the stool in his corner.
Marquez finally had a victory over his rival, his first in the four-fight series. He did it with his explosive counterpunching power. Pacquiao had been going for a knockout of his own, and he left himself wide open.
Marquez took advantage of that opening as few fighters have ever done on the biggest stage.
The strength and power that Marquez displayed Saturday night at the MGM Grand in Las Vegas had not been on display in his three previous fights with Pacquiao.
Marquez had not knocked down Pacquiao even one time during their previous 36 rounds of action.
Somehow, at the age of 39, Marquez found the power to knock Pacquiao down twice. The second of those knockdowns was so powerful that it looked as though he had channeled his inner Rocky Marciano.
It's unusual for fighters to thrive once they get past their 35th birthdays. It's not impossible, as boxing fans have seen many great fighters who have survived on skill, savvy and ring generalship as they have approached the age of 40 and gone beyond.
Archie Moore thrived during the 1950s after the age of 35, and James "Lights Out" Toney has done the same more recently.
However, those fighters did not come into the ring looking more muscular and cut up than they had when they were in their 20s and early 30s the way Marquez did against Pacquiao.
Questions have to be asked about how Marquez got in such impressive condition.
The times dictate those questions. Athletes have been using performance-enhancing drugs for decades. That includes boxers.
But there are additional questions to ask Marquez. He hired Angel Guillermo "Memo" Heredia as his strength and conditioning coach prior to his third bout with Pacquiao. Marquez was much bigger for the fourth fight than he was 13 months ago.
Heredia admits that in the past, he has supplied athletes with performance enhancers like steroids and human growth hormone. He also avoided prosecution in the BALCO steroids case by testifying for the government (source: Yahoo! Sports).
Heredia says that he now does things the right way and that all his clients are drug free. That includes Marquez, who told Yahoo! that Heredia has helped bring him vitality and strength.
"In working with Angel, I've changed everything," Marquez said. "I feel great. I feel great because I've had a 20-year career, and I did it the same way for 18 years. But now, Angel has changed everything."
Marquez certainly has the look of a stronger and more well-defined athlete.
He got the results he wanted when his big right hand crashed into Pacquiao's jaw and put him to sleep in the sixth round.
The question is how he got the strength to get that kind of result in the ring.
Questions need to be asked.
Answers need to be given.