Article continues below advertisementDiane Keaton's cause of death has been revealed.Just four days after the actress passed away, a news outlet confirmed that she died from pneumonia at age 79.Article continues below advertisementSource: MEGADiane Keaton died from pneumonia."The Keaton family are very grateful for the extraordinary messages of love and support they have received these past few days on behalf of their beloved Diane, who passed away from pneumonia on October 11," a statement from Keaton's family read.