Cause of death: heart attack
David O. Selznick (born David Selznick: May 10, 1902 – June 22, 1965) was an American film producer, screenwriter and film studio executive who produced Gone with the Wind (1939) and Rebecca (1940), both of which earned him an Academy Award for Best Picture. He also won the Irving Thalberg Award at the 12th Academy Awards, Hollywood's top honor for a producer, in recognition of his shepherding Gone with the Wind through a long and troubled production and into a record-breaking blockbuster.
The son and son-in-law of movie moguls Lewis J. Selznick and Louis B. Mayer, Selznick served as head of production at R.K.O. Radio Pictures and went on to become one of the first independent movie producers. His first wife was Mayer's daughter Irene Selznick, who became a highly successful Broadway producer after their divorce, and his second wife was Oscar-winning actress Jennifer Jones.
Source : Wikipedia