Here's one more, in regards to the involvement of George A Smith and Brigham Young. Here's the quote from Massacre, page 70:
In after years Smith’s journey to southern Utah became a matter of controversy, with some interpreting his sermons and even the places he stopped as a deliberate prelude to the Mountain Meadows Massacre less than a month later. John D. Lee’s several posthumously published “confessions” – which appeared two decades after the tour – said that while the party was passing through the Santa Clara canyon, Smith asked, “Brother Lee, what do you think the brethren would do if a company of emigrants should come down through here making threats? Don’t you think they would pitch into them?”
“They certainly would,” Lee replied, to which Smith answered, “I asked Isaac (meaning Haight) the same question, and he answered me just as you do.
Several months after the first publication of the this conversation, another version of Lee’s confessions appeared under the title Mormonism Unveiled. It made the charge against Smith even stronger. “I have always believed, since that day, that General George A. Smith was then visiting Southern Utah to prepare the people for the work of exterminating Captain Fancher’s train of emigrants,” the book said, “and I now believe he was sent for that purpose by the direct command of Brigham Young.” The passage would be used by some writers as key evidence for saying that Smith and Young had planned the massacre.
These statements, however, would have required remarkable prescience on Smith’s part. Even if he knew which trains would take the northern or southern routes to California, it is doubtful he knew their behavior on the road would include making threats against the southern Utah people. Moreover, Lee’s attorney and editor, William W. Bishop, almost certainly reworked Lee’s “confessions” in Mormonism Unveiled to improve its sales, including the charges against Smith and Young. Bishop had a motive before making these changes as his legal fees were tied to the book’s royalties.
Just moments before Lee’s execution – and after he had supposedly written the words in Mormonism Unveiled – Lee talked with a reporter from the then unabashedly anti-Mormon Salt Lake Tribune. The reporter pressed Lee to know what Smith had said to him before the massacre.
“Did he preach hostile to the emigrants?” the reporter asked.
“He was visiting all the settlements and preaching against the emigrants,” Lee said. Then referring to the people killed at Mountain Meadows, he added, “I don’t know that he meant those particular emigrants.” This – Lee’s final statement on the subject – makes it unlikely that he made the statement attributed to him in Mormonism Unveiled, especially since he had been offered his life by prosecutors if he would just charge Smith and Young with ordering the massacre. He went to his death instead.
Here's the passage discussing the same event from Bagley. I have highlighted the portion omitted in Massacre which I find pertinent, page 86:
Smith claimed that he enjoyed his “glorious interview” with the natives of the desert, but Lee found the large numbers of Paiutes that gathered around the Mormons impudent. As Lee translated, the apostle told them the Americans were their enemies and the enemies of the Mormons too. If the Indians helped to fight their mutual adversary, the Saints “would always keep them from want and sickness and give them guns and ammunition to hunt and kill game with, and would also help the Indians against their enemies when they went into war.” This pleased them, Lee recalled, “and they agreed to all that [he] asked them to do.”
During their visit to the Tonaquints, Lee thought Smith was a little fearful of the Indians. Lee hitched up quickly and left. “Those are savage looking fellows,” Smith said after a mile or so. “I think they would make it lively for an emigrant train if one should come this way.” Lee said the Paiutes would attack any train. Smith went into a deep study and said, “Suppose an emigrant train should come along through this southern country, making threats against our people and bragging of the part they took in helping to kill our Prophets, what do you think the brethren would do with them? Would they be permitted to go their way, or would the brethren pitch in and give them a good drubbing?” Lee said the brethren were under the influence of the Reformation and were still red-hot for the gospel. Any train would be attacked and probably destroyed. “I am sure they would be wiped out if they had been making threats against our people.”
Smith seemed delighted with Lee’s answer and rephrased the question, “Do you really believe the brethren would make it lively for such a train?” Lee said they would, and he warned that unless Smith wanted the Saints to attack every train passing through the south, Brigham Young should send direct orders to Dame and Haight to let them pass. The people, Lee said, were bitter, full of zeal, and “anxious to avenge the blood of the Prophets.” Smith said he had asked Haight the same question, and Haight gave the same answer. Smith thought the Paiutes, “with the advantage they had of the rocks, could use up a large company of emigrants, or make it very hot for them.” Lee again warned that if Young wanted emigrants companies to pass unmolested, he must give Dame and Haight explicit instructions “for if they are not ordered otherwise, they will use them up by the help of the Indians.” The conversation convinced Lee that Smith expected every emigrant passing through the territory to be killed. I thought it was his mission to prepare the people for the bloody work,” Lee wrote.
Federal investigators were later convinced Brigham Young sent letters south “authorizing, if not commanding,” the destruction of the Fancher train, but it is unlikely Young would commit such an order to writing. Lee’s tale of his ambiguous conversations with Smith on the Santa Clara may best reflect what actually happened. If Smith gave orders to kill the emigrants, they may have been no more explicit than to “use them up” or “give them a good drubbing.” Mormon leaders often spoke in code words whose meaning was clear only to insiders. One of Young’s favorite phrases, “A word to the wise is sufficient,” meant, “Don’t make me spell it out.” This ambiguity had many advantages; it sheltered Mormon leaders from accountability and shifted responsibility from top leaders to local authorities. But orders couched in such enigmatic terms were easily misinterpreted, a serious problem given the volatile atmosphere and the slow pace of communications in Utah Territory.
Lee arrived at his own conclusion: “I have always believed, since that day, that General George A. Smith was then visiting Southern Utah to prepare the people for the work of exterminating Captain Fancher’s train of emigrant, and I now believe he was sent for that purpose by the direct command of Brigham Young.”
Again, see the difference?