He had been hospitalized with a "serious, but stable medical condition," according to his son Christian Gregory. Christian Gregory had posted details about his father's illness on his dad's Instagram account.
Gregory had fallen ill on Aug. 9, was hospitalized for a short time and then released before going back on Aug. 12, according to a post.
Gregory started his career as a comedian while serving in the military in the 1950s. He then went on to to appear on television. During the 1960s, Gregory began fighting for civil rights.