Roberts hatched a plan which was approved, according to Madsen, by the First Presidency "two elders would be sent to the 'courthouses in the county seats to give them information on the historical, social, political and religious phases of the work of the Lord.' Roberts picked Elder John H. Gibbs as the first of the two missionaries, but according to Madsen, the second missionary was Elder William S. Berry.
Madsen also ascribed additional significance to his death because of the "irony that his two appointed 'peacemakers' were the ones who had been shot down." But Elder Gibbs companion was William Howell Jones, not Elder Berry. This is made clear from every original source, including the journals of Elder Gibbs and Berry, and the writings of Elder Jones. Elder Jones was also at the masscare, and survived to describe his role.
That isn't the only error I found, but the others were understandable, considering Madsen was working with Roberts own writings. And erros in Roberts writing would be a whole other post. Some of the errors in Madsen's book are a matter of opinion, so aren't worth addressing it here. While I love reading his material and still suggest you read this book, I have to wonder what other errors there might be.
With Elder Gibbs, Roberts assigned William S. Berry, at forty-six a mature and seasoned missionary and a native of Tennessee. Roberts described him as "somewhat slow of speech, but endowed to a remarkable degree with good sound sense, and of a mild and genial disposition," a man who spoke and acted out of practical wisdom. With dedication not uncommon in that era, he had come on his two-year mission, leaving behind a family of fifteen children.