Siphesihle Mntungwa made the troubling admission this week to Sowetan Live, a daily newspaper in South Africa, saying he's received threats and horrible messages accusing him of causing the 24-year-old's death during their sanctioned bout on Sunday.

"I came under heavy criticism and insults on social media platforms when Simiso was hospitalised," Mntungwa said, "it has taken another level now that he has passed away."

"I just can't take it anymore. One thing is left for me -- I am going to kill myself."

Mntungwa went on to say that he did not kill Simiso, nor was it his intention to end the fighter's life. Rather, the 27-year-old said he was just competing in a boxing match, focusing on winning the title so he could provide for his family financially.

"I did not kill Simiso," he said. "We may have been involved in a boxing fight but it was not a matter of life and death."

"All I wanted was to win the title, which maybe was going to help change my life and that of my family."

As we reported, Simiso became so disoriented during the 10th round of the contest with Mntungwa in South Africa that he began punching thin air -- forcing the referee to end the match.

Simiso, who collapsed in the ring following the scary scene, was rushed to the hospital ... but unfortunately, later died there.

Mntungwa's trainer, Mmeli Mkhize, said he's seeking professional help for Mntungwa following the fighter's disturbing admission to the outlet.

He added that the threats against Mntungwa have been so bad, they can't even pay their respects to Simiso out of concern for what people might try to do them there.

"We will not even be able to attend the funeral because we are scared," he said.