Cause of death: heart attack
David Fitzgerald Doyle (December 1, 1929 – February 26, 1997) was an American actor. He was best known for his portrayal of John Bosley on the 1970s TV series Charlie's Angels. Doyle and Jaclyn Smith were the only actors to appear in every episode of the show. Doyle also became known later as the first voice of Grandpa Lou on the Nickelodeon series Rugrats.
Source : Wikipedia
