Gast studied dramatic arts at Columbia University, but dropped out without earning a degree in order to join a crew involved with the 1957-60 TV series "High Adventure With Lowell Thomas" which went on locales throughout the world. In the early 60s, he developed a reputation as a prominent photographer, often of fashion layouts, working for such magazines as ESQUIRE, VOGUE and HARPER'S BAZAAR. Although continuing in this line into the 70s, Gast also turned his attentions to documentary filmmaking. He exhibited a flair for musical subjects as evidenced by his "Our Latin Thing" (1972) and "Salsa" (1977) both anticipated the influence Latin American music would have on greater American pop culture during that decade (e.g., the Hustle dance craze). In 1977, Gast and Jerry Garcia co-directed "The Grateful Dead" concert and tour film, and Gast, Richard Chase, and Kevin Keating directed "Hells Angels Forever" (1983), the definitive work on the motorcycle clique. One of Gast's most mainstream forays was his editing and co-producing of the 1993 NBC docudrama "Fallen Champ: The Untold Story of Mike Tyson," a telefeature which chronicled Tyson's rise to heavyweight champion and his conviction on rape charges. Working in the milieu of prize fighting and concert films was a prelude to "When We Were Kings" and aided in his being hired for the job. During the period, Gast also worked with Barbara Kopple editing several of her award-winning projects. The pair worked for over two years on "Woodstock 94," an uncompleted documentary on the reunion of the late 60s event. Propaganda Films withdrew its financial support at the last minute, leaving the film in limbo.