Ferguson took the internet by storm in the early days of viral videos as his street fighting videos became the stuff of legend.
The heavyweight fighter fought as a professional boxer and as a mixed martial artist in both UFC and Bellator MMA.
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Coral Springs police later confirmed to ESPN that Ferguson had been hospitalized but dispelled reports that it was the result of an incident at his home.
MMA reporter Ariel Helwani later confirmed Ferguson’s hospitalization, saying that the situation didn’t look good.
"Can confirm reports that Kimbo Slice was admitted to a local Fla. hospital. I'm told at this time that he's not in good shape, sadly," Helwani wrote on Twitter.
Ferguson's last fight was a TKO of Dhafir Harris, aka Dada 5000, another fighter who came out of the Miami street fight scene.
The Ferguson vs. Harris fight was eventually ruled a no contest after Ferguson failed a drug test.
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Bellator MMA later confirmed the news to of Ferguson's death.
Ferguson was scheduled to fight James Thompson at Bellator 158 in July in London.
Kevin "Kimbo Slice" Ferguson was 42 years old.