Elizabeth Kane was at Brigham Young's side on Sunday night, August 26, 1877. Young wished to pass on his presidential calling to his son Apostle John Willard Young in a dynastic bid, but that summer, he had confessed to his father that he couldn't stand his first wife and instead planned to court and marry Luella Van Cott Cobb, the 16 year-old granddaughter of Brigham's third wife, Augusta Cobb. According to Elizabeth Kane's notes, this was the topic of Brigham Young's last "intelligent thinking, and speech." Brigham spoke to John "about Cobb girl" and told him that she was "Of a bad Tribe." And "herself too of the kind fond of embroidered underclothes." Brigham reponded to a whipered request. The "Answer" was, "If you cannot feel to marry...well! Ah Johnny!" Young then immediately fell into a comatose state, which Kane said he never emerged from, before passing away on August 29, 1877 at 4:00 pm.
[Source: Elizabeth Kane notes as described by Connell O' Donnovan]