Brazilian MMA fighter Allan Nascimento died Monday after suffering a heart attack as he slept, the UFC said.

He was 34.

The “beloved flyweight fighter” was “found unresponsive after suffering an apparent heart attack in his sleep,” according to a statement from UFC.

“Despite the efforts of the responding medical team, he was pronounced deceased at the scene,” the UFC continued. “Our thoughts and deepest condolences are with Allan’s family, friends, teammates, and loved ones during this incredibly difficult time.”

The 5-foot-8, 125-pound Nascimento went 22-7 in his UFC career that dated to 2011.

He lost his last bout in a split decision to Mitch Raposo on June 20 in Las Vegas.

Nascimento’s sudden death stunned the mixed martial arts community.

“Today I lost a brother — a guy who was truly one of a kind — and the pain is unbearable,” No. 3-ranked lightweight and longtime friend Charles Oliveira said in a statement.

Brazilian middleweight Caio “The Natural” Borralho called Nascimento “one of the most kind fighters that’s I’ve ever met!”

“Polite, good energy and always in good spirits! He will be missed,” he said in a social media post.

And UFC correspondent Evelyn Rodrigues called Nascimento one of “the kindest souls I’ve ever had the privilege of knowing through MMA. Rest in peace, Allan.”