Thabete - who hailed from Umlazi in KwaZulu-Natal, South Africa - had been playing to the crowd before a contest on the weekend. He walked out slowly towards the centre of the gymnasium before breaking into a trot and waving his arms, encouraging spectators to cheer him on.
He ran into the centre of the mat and launched into the backflip before hitting his head. Thabete lay motionless on his side before rolling onto his back.
The first man to attend to him lifted his legs up before several others joined in to help.
Vision of the accident went viral on the internet before the severity of the damage was made public.
South African bodybuilding magazine Muscle Evolution said the bodybuilding community was "shocked and saddened" by the news of Thabete's death.
The magazine reports he was an International Federation of Bodybuilding and Fitness (IFBB) Junior World Champion in the up-to 75kg category who recently won an event at the IFBB Muscle Mulisha Grand Prix in July.
Thabete came first in the Under-23, over 75kg division of the competition held in Johannesburg, where he successfully performed a backflip during his routine.
Thabete also finished runner-up in the division for senior men up to and including 80kg.
Friends went to social media to pay tribute to Thabete.
Its sad that his work only becomes recognised by his accident and no one cared the least to post about him when he was on the rise trying to stand out and be the best.... R.I.P ntwana World Champ
Posted by IRON Soldiers on Thursday, 10 August 2017
