28-year-old Russian boxer Maxim Dadashev died on Tuesday, four days after suffering a brain injury in a fight in Maryland.

The Russian Boxing Federation said Dadashev suffered a brain swelling in Friday’s light-welterweight fight with Subriel Matias at the Theater at MGM National Harbor in Oxon Hill, Maryland. He underwent emergency brain surgery but his heart stopped on Tuesday, the federation said.

Dadashev, known as “Mad Max,” was unable to walk to the dressing room and was immediately hospitalized at UM Prince George’s Hospital Center shortly after the fight, which was stopped by his corner following the 11th round after Dadashev took numerous shots to the head.

Footage from the fight shows Dadashev shaking his head in his corner as his trainer, Buddy McGirt, pleads with him to stop the fight, telling him: “You’re getting hit too much, Max. Please, Max, please let me do this.” Shortly after, the referee stopped the fight at McGirt’s request.

The Russian Boxing Federation’s secretary general, Umar Kremlev, said the federation would investigate whether anyone was at fault for Dadashev’s death. He added the federation would give Dadashev’s family financial support.