UFC fighter Allan Nascimento has died at the age of 34 after an apparent heart attack, the promotion announced. Nascimento, a flyweight, was found unresponsive in his sleep and was pronounced dead at the scene, the UFC said. The Brazilian veteran compiled a 4-2 record inside the UFC Octagon during his career. The cause of death remains under investigation, and officials have not confirmed whether the heart attack was the definitive cause. The UFC expressed condolences to Nascimento's family, friends, and teammates in a statement. Nascimento had been competing professionally in mixed martial arts for several years before joining the UFC, where he built a reputation as a durable and competitive flyweight. His death marks a sudden loss for the MMA community, which has seen several fighters pass away at relatively young ages in recent years. No further details about the circumstances were immediately available, and the UFC said it would not comment further out of respect for the family's privacy.