Amuson came in with a record time of 12.12 seconds, beating Kendra Harrison’s 2016 record of 12.20 seconds by 0.8.
She won the gold medal in the final, although her initial time of 12.06 was over due to high wind speed.
Amusan’s world record shook the athletics world.
In November 2016, the now 25-year-old tweeted: “Unknown now but soon I’ll be unforgettable, I’ll persist until I succeed.”
“When I saw it on screen after the semi-finals, I couldn’t believe it. But it was just a matter of time,” Amusan told reporters on Sunday.
But some expressed skepticism over the race, which saw many of the competitors clocking in at their best.
“All the athletes looked shocked,” said the former 200 and 400-meter runner.
“Heat 2 first showed us a winning time of 12.53. A few seconds later it shows 12.43. It’s normal to drop below .01. .10 is not,” he said.
Johnson received a swift and fierce response to his comments, and later returned to Twitter to clarify further, pointing out that he predicted Amuson would win.
“My job as a commentator is to comment. I was attacked, accused of racism, and one athlete questioning the timing of 28 athletes (not 1 athlete) wondering whether the timing system was flawed. Questioned the brilliance of which I respect and predict. To win. Unacceptable. I move on,” he said.
CNN has reached out to World Athletics for comment.