Shortly before the martyrdom, Joseph Smith said, “I am going like a lamb to the slaughter.”

Doctrine and Covenants 135:4–5

4 When Joseph went to Carthage to deliver himself up to the pretended requirements of the law, two or three days previous to his assassination, he said: “I am going like a lamb to the slaughter; but I am calm as a summer’s morning; I have a conscience void of offense towards God, and towards all men. I shall die innocent, and it shall yet be said of me—he was murdered in cold blood.”—The same morning, after Hyrum had made ready to go—shall it be said to the slaughter? yes, for so it was—he read the following paragraph, near the close of the twelfth chapter of Ether, in the Book of Mormon, and turned down the leaf upon it:
5 And it came to pass that I prayed unto the Lord that he would give unto the Gentiles grace, that they might have charity. And it came to pass that the Lord said unto me: If they have not charity it mattereth not unto thee, thou hast been faithful; wherefore thy garments shall be made clean. And because thou hast seen thy weakness, thou shalt be made strong, even unto the sitting down in the place which I have prepared in the mansions of my Father. And now I . . . bid farewell unto the Gentiles; yea, and also unto my brethren whom I love, until we shall meet before the judgment-seat of Christ, where all men shall know that my garments are not spotted with your blood. The testators are now dead, and their testament is in force.

“While the years in Nauvoo provided many happy times for the Saints, persecution soon began again, culminating in the murder of Joseph and Hyrum Smith. This was a dark and mournful time never to be forgotten. Recording her feelings upon hearing of the martyrdom, Louisa Barnes Pratt wrote: ‘It was a still night, and the moon was at the full. A night of death it seemed, and everything conspired to make it solemn! The voices of the officers were heard calling the men together and coming in the distance made it fall on the heart like a funeral knell. The women were assembled in groups, weeping and praying, some wishing terrible punishment on the murderers, others acknowledging the hand of God in the event’ [“Journal of Louisa Barnes Pratt,” Heart Throbs of the West, comp. Kate B. Carter, 12 vols. (1939–51), 8:231].

“Like Louisa Barnes Pratt, many Latter-day Saints remembered the events of 27 June 1844 as a time of tears and broken hearts. The martyrdom was the most tragic event in the Church’s early history. However, it was not unexpected.

“On at least 19 different occasions, beginning as early as 1829, Joseph Smith told the Saints that he would probably not leave this life peacefully [History of the Church, 4:587, 604; 6:558]. While he felt that his enemies would one day take his life, he did not know when. As the spring of 1844 became summer, enemies both within and without the Church worked toward Joseph’s destruction. Thomas Sharp, editor of a nearby newspaper and a leader in Hancock County’s anti-Mormon political party, openly called for the Prophet’s murder. Citizens’ groups, apostates, and civic leaders conspired to destroy the Church by destroying its prophet.

“The governor of Illinois, Thomas Ford, wrote to Joseph Smith, insisting that the city council members stand trial before a non-Mormon jury on a charge of causing a civil disturbance. He said that only such a trial would satisfy the people. He promised the men complete protection, although the Prophet did not believe he could fulfill his pledge. When it appeared that there were no other alternatives, the Prophet, his brother Hyrum, John Taylor, and others submitted to arrest, fully aware that they were guilty of no crimes.

“As the Prophet prepared to leave Nauvoo for the county seat of Carthage, about 20 miles away, he knew that he was seeing his family and friends for the last time. He prophesied, ‘I am going like a lamb to the slaughter, but I am calm as a summer’s morning’ [History of the Church, 6:555].”

(Our Heritage: A Brief History of The Church of Jesus Christ of Latter-day Saints [1996], 62–63.)