[2] Vaughan was opposed to a national Prohibition on the manufacture, transportation, sale, possession, and consumption of alcoholic beverages.

[1] He was relocated to Honolulu in the Territory of Hawaii on October 1, 1915, when he was appointed assistant United States district attorney.

Their only son US Navy Lt. Robert Louis Vaughan (1892–1920) died in a plane crash related to his military service.

Believed to be despondent over the death of his son, Horace Vaughan was found on November 10, 1922, in his Honolulu home with a bullet wound to his neck and a gun by his side, an apparent suicide.

[8] Youngest daughter Jean Vaughan Gilbert (1904–1975) was one of the first women lawyers in Hawaii, and became city attorney of Honolulu.