Today marks 50 years since the Altamont Festival, which became famous for the wrong reasons.

Four people died at the festival, including one who was fatally stabbed by a member of the Hells Angels, Alan Passaro. Passaro was charged with murder but later acquitted on grounds of self-defence.

Joel Selvin, author of Altamont: The Rolling Stones, the Hells Angels, and the Inside Story of Rock's Darkest Day, explains the legacy of the disastrous concert.

Video by Cody Godwin and Shrai Popat