Slice parlayed videos of his street fights into a career as an MMA fighter. He reportedly died Monday at a Florida hospital of as-yet-undisclosed causes.
As some MMA fans suspected, the 27-year-old Dublin native's retirement announcement was simply a maneuver to gain leverage in his contract disagreement with the UFC.
McGregor made the announcement on Twitter, but some MMA fans are questioning whether the brash 27-year-old fighter means what he says or if this is simply a move to get more money from UFC.
The state was the last in the country to end its ban on MMA. The Ultimate Fighting Championship, a league that hosts MMA fights, has already scheduled a match at Madison Square Garden.