The 53-year-old New York City native collapsed during a performance in New Haven County at the Hamden Town Center Park, according to authorities.
He was rushed to a nearby hospital, where he was pronounced dead.
His tour manager, Birch Michael, posted a statement on Facebook: "It is with the heaviest of hearts I announce the passing of Isaac Freeman III, Known professionally as Fatman Scoop. You taught me how to be the man I am today.
"I Love you Scoop, Thank you so much for everything you gave to me. Rest In Peace."
The cause of death has not yet been announced.
Freeman gained notice for his appearances on the singles "It's Like That" by Mariah Carey and "Lose Control" by Missy Elliott.
He also appeared as himself on the TV series "The Boondocks."
This is a developing story. Check back to Daily Voice for updates.
Click here to follow Daily Voice Kings Park and receive free news updates.