Ultimate Fighting Championship star Allan Nascimento died Monday in his sleep after “an apparent heart attack,” the organization announced on social media. The Brazilian flyweight fighter, who is survived by his wife and two children, was 34 years old.“This morning, Monday, August 3rd, our beloved flyweight fighter, Allan Nascimento, was found unresponsive after suffering an apparent heart attack in his sleep,” wrote the mixed martial arts organization on Instagram and X.The company continued, “Despite the efforts of the responding medical team, he was pronounced deceased at the scene. Our thoughts and deepest condolences are with Allan’s family, friends, teammates, and loved ones during this incredibly difficult time.”Nascimento fought just six weeks ago in Las Vegas, Nevada, and was defeated by fellow UFC fighter Mitch Raposo after three rounds in a split-decision loss. “Unfortunately, victory didn’t come this time, a defeat by split decision of the referees, but I leave with my head held high, knowing that I gave my best out there,” he wrote according to an Instagram translation after the fight. “Defeats also teach, strengthen, and are part of the journey.”He continued, “Thank you all for the affection and messages.”Nascimento was born in São Paulo and began his professional MMA career in 2011, starting out in the Japan-based RIZIN organization. He signed with the UFC in 2021 and died with a UFC record of 22-7 — with 16 of those wins the result of his formidable submission work.On Instagram in June, Nascimento recalled starting training in Muay Thai in 2007 when he was just a “skinny, tiny guy.” He remembered being nicknamed “Puro Osso,” or “Pure Bone,” and that his parents were “totally against” his life as a fighter — until they saw him succeed and “liked it.”Nascimento punching Raposo during their flyweight fight in Las Vegas in June.Chris Unger/Zuffa LLC/Getty ImagesNascimento spent much of his career training at the São Paulo MMA gym Chute Boxe Diego Lima with former UFC lightweight champion Charles Oliveira, who on Tuesday shared an Instagram Reel showcasing Nascimento’s dedicated workouts and sparring sessions.“Today, our team loses much more than an athlete; we lose a warrior, a friend, a dedicated competitor, and an extraordinary human being who earned the respect and admiration of all who had the privilege of knowing him,” Oliveira wrote according to an Instagram translation.He continued, “Allan inspired both on and off the mats with his determination, humility, respect, and fighting sprit. His presence will leave an immeasurable void. Rest in peace, Allan. Your name, your story, and your legacy will live on forever through our star.”Fellow fighters, fans and MMA personalities have shared their condolences since Monday’s announcement, including UFC international correspondent Evelyn Rodrigues, who wrote on Instagram: “One of the kindest souls I’ve ever had the privilege of knowing through MMA.”UFC fighter Caio Borralho wrote, “He will be missed.”