LOUISVILLE, Ky. (WHAS11) – An amateur mixed martial arts fighter died Saturday night after losing a match at Louisville’s Expo Five Center.

Donshay White, 37, of Radcliff, was competing in a heavyweight fight hosted by Hardrock MMA when his condition deteriorated. The referee called the fight when his opponent, Ricky Muse, delivered several punches and it became clear White could no longer defend himself.

White collapsed shortly after he got to the locker room. In a statement, the Kentucky Boxing and Wrestling Commission said White was treated immediately after his fight by a licensed ringside physician and first responders, then received onsite care before he was rushed to Sts. Mary and Elizabeth Hospital where he died.

“Our thoughts are with the family and friends of Donshay White following his passing,” the statement said. “The health and safety of Kentucky’s combat sports athletes is the highest priority of the Kentucky Boxing and Wrestling Commission, and the commission is reviewing all of the details surrounding this tragic event."

The coroner has not determined an official cause of death, however, those close to White said it was believed to be some type of cardiac trouble.

“It was sheer exhaustion," said Billy Smith, who was White's trainer and cornerman for a fight in November 2015. White won that fight with a knock-out in the first round.

Smith said he was not able to be White's cornerman for Saturday's fight due to a scheduling conflict.

“When you’re that age and you haven’t trained, your heart is not prepared, and you get in there – all we see is the will of the person. We don’t know what’s going on inside that chest," Smith said. “Everybody is just astonished this happened. It’s just not something that happens. This is a rare, rare incident."

Smith said White's death would be felt across the fighting community, describing the amateur fighter as "respectful" and "humble."

“Hardrock MMA joins the entire MMA community in mourning Donshay White," the organization said in a statement posted to Facebook. "As a promotion who has put together 89 events over the last 8 years without incident, we always have and we will continue to put our fighters safety above all else. Our thoughts and prayers go out to his family and loved ones."