If you want to read more about this topic a good book is, "Mormonism, Mama and Me" by Thelma Geer. She is a descendant of John D. Lee. The book is a free download on a Kindle. Very enlightening. I just recently finished reading it.
ALL: BTW, I discovered this 2003 thread about Sally Denton's book on the Mountain Meadows Massacre: Mountain Meadows massacre analysis ends with an accusation
Here is a quote from the article in that thread: Denton comes even closer to saying Young knew in advance and probably ordered the killings. She gets as close to making that charge as a serious scholar can (and this book, regardless of whether you agree with the author's conclusions, is indeed serious scholarship) without a signed confession. She repeatedly calls Young a dictator, depicts him as mean-spirited and claims he lied when he denied that Mormons perpetrated the killings...Young from office. Young had been appointed governor of Utah Territory by President Millard Fillmore and ran Utah more as a theocracy than as a territory of the United States. Buchanan intended to establish U.S. authority over Utah. Young responded by putting Utah under martial law, ordering the destruction of army supplies and preparing to go to war with the United States. Under any reasonable definition of the term, he was guilty of treason. Buchanan avoided a shooting war between Utah and the United States partly by promising Young and other Mormon leaders a pardon from charges of treason. The war was averted, but the massacre had taken place. Brooks wrote near the end of her book, "While Brigham Young . . . did not specifically order the massacre, [he] did preach sermons and set up social conditions which made it possible." Bagley wrote, "As long as modern [church leaders] deny that the LDS church had 'any complicity in the occurrences of that fateful day,' they can never come to terms with the truth." Denton writes, "Within the context of the era and the history of Brigham Young's complete authoritarian control over his domain and his followers, it is inconceivable that a crime of this magnitude could have occurred without direct orders from him."