UFC fighter Allan Nascimento, a Brazilian flyweight known by the nickname “Puro Osso,” has died at the age of 34, the Ultimate Fighting Championship announced Monday. The promotion stated that Nascimento was found unresponsive on Monday morning, having apparently suffered a heart attack in his sleep. Medical teams responded to the scene but could not revive him.

Nascimento last competed in June at the UFC Fight Night: Kape vs. Horiguchi event, where he lost a split decision to Mitch Raposo. He first gained attention on “Dana White’s Contender Series” in 2018, a show where the UFC president identifies emerging talent. Although he lost his debut on the show to Raulian Paiva via split decision, Nascimento still secured a place on UFC cards.

During his time with the UFC, Nascimento compiled a professional record of 4-2 and earned Fight of the Night performance bonuses on two occasions. As a professional fighter, the 5-foot-8, 125-pounder had a career record of 22-7.

Nascimento trained at Chute Boxe in São Paulo, a gym that has produced numerous notable fighters. Charles Oliveira, a fellow fighter from the gym, shared tributes to Nascimento on social media, calling him a brother and a legend. Oliveira expressed his gratitude for their time together, both on the mats and in the corner during fights.