UFC flyweight fighter Allan Nascimento reportedly died suddenly on Monday at age 34 after suffering a heart attack. Reports said the São Paulo native died in his sleep.

Nascimento would have turned 35 in September, according to ESPN Brazil, which reported on his death. The news has drawn attention across the mixed martial arts community because of the fighter’s age and the sudden nature of his passing.

Nascimento was known as a flyweight competitor associated with the UFC. Details available in the initial reports remained limited, and no further circumstances were provided in the supplied coverage.