Former UFC champion Francis Ngannou said in a social media post on Monday that his 15-month-old son Kobe died.

Ngannou, an MMA fighter and heavyweight boxer, revealed his young child's death in a heartbreaking tribute on Instagram, saying his "little boy, my mate, my partner Kobe was full of life and joy."

"I was my best self next to him and now I have no clude of who I am," he wrote. "Life is so unfair to hit us where it hurts the most."

"How do you deal with such a thing?" Ngannou added. "How can you live with it? Please help me if you have an idea because I really don't know what to do and how to deal with this." 

The 37-year-old did not disclose his son's cause of death.

"What's the purpose of life if what we're fighting tooth and nail to get away from is what finally hit us the hardest!?" he said in a different post. "... Why does life always take what we don't have? I'm f---ing tired."

Many fighters, including UFC legend Conor McGregor, expressed their condolences to Ngannou.

"I am so sorry to hear of your loss Francis, my prayers are with you and your family at this time," McGregor said.

Ngannou's manager, Marquel Martin, said in an Instagram post that he's "absolutely heartbroken" for him.

"You have an Angel on your side," Martin said. "And he's with you everyday ... cheering on his dad and watching him continue to impact the world for the better."

After rising from poverty in Cameroon and homelessness in France, Ngannou became known for his powerful punches and reached the mountaintop of the professional fighting world. He was the reigning UFC heavyweight champion before leaving the league and becoming a boxer. He endured a knockout loss against Anthony Joshua in March and took another loss last year against World Boxing Council heavyweight champion Tyson Fury.

Ngannou's next fight will be against Renan Ferreira in the Professional Fighters League.

In:
• MMA
• Death
• Boxing

Christopher Brito

Christopher Brito is a social media manager and trending content writer for CBS News.