Joseph Smith and his brother Hyrum were murdered in Carthagfe Jail. An excellent account of the event is available on wikipedia here: Death of Joseph Smith Jr
I would add to this the account of William M. Daniels. He was the prosecutions key witness during the trial of the murder of Joseph and Hyrum. Shortly before the trial he published a pamphlet with his testimony of the events. He states that Thomas C. Sharp had given a rallying speech after the Governor had given an order for the Militia to disband. Sharp stated that the law "is insufficient" for their problem and that they must take matters into their own hands to end "the mad carreer of the Prophet." They should murder the Smiths in Carthage and have the news reach Nauvoo while the governor was still there. The enraged Mormons will fall upon and murder Tom Ford and "we shall be rid of the damned little Governor and the Mormons too." At this Captain Grover and eighty-four others stepped forward.
The mob had blackened their faces with wet gunpowder. Daniels account gives the familiar account took place as the mob ran up the stairway, adding that the pistol Joseph fired into the mob "wounded three of them."
With Hyrum dead and the others wounded Joseph Sprang to the window, hoping to draw the attention away from his friends who were still alive in the room. Seeing an array of bayonets below, he caught the window casing and hung there by his hands and feet for a few minutes before he fell to the ground. While he ws hanging Colonel Williams shouted "Shoot him! God damn him! Shoot the damned rascal!" However, according to Danials, no one fired at him. Presently he fell to the ground, landing on his back and right shoulder.
he rolled instantly on his face. From this position he was taken by a young man, who sprang to him from the other side of the fence, who held a pewter fife in his hand, - was bare-foot and bare-headed, having on no coat - with his pants rolled up above the knees, and shirtsleeves above his elbows. he set President Smith against the south side of the well-curb, that was situated a few feet from the jail.
When President Smith had been set against the curb, and began to recover, Col. Williams ordered four men to shoot him. Accordingly, four men took an eastern direction, about eight feet from the curb, Col. Williams standing pertly at the rear, and made ready to execute the order. While they were making preparations, and the muskets were raised to their faces, president Smith's eyes rested upon them with a calm and quiet resignation. He betrayed no agitated feelings and the expression upon his countenance seemed to betoken his inly prayer to be, "O, Father, forgive them, for they know not what they do."
The fire was simultanious. A slight cringe of the body was all the indication of pain that betrayed when the balls struck him. He fell upon his face.
The ruffian, of whom I have spoken, who set him against the well curb, now secured a bowie knife for the purpose of severing his head from his body. he raised the knife and was in the attitude of striking, when a light, so sudden and powerful, burst from the heavens upon the bloody scene, (passing its vivid chain between Joseph and his murderers,) that they were struck with terrified awe and filled with consternation. This light, in its appearance and potency, baffles all powers of description. The arm of the ruffian, who held the knife, fell powerless; the muskets of the four, who fired, fell to the ground, and they all stood like marble statues, not having the power to move a single limb of their bodies.
by this time most of the men had fled in great disorder. I never saw so frightened a set of men before. Col. Williams saw the light and was also badly frightened; but he did not entirely lose the use of his limbs or speech. Seeing the condition of these men, he hallooed to some who had just commenced a retreat, for Gods sake to come and carry off these men. They came back and carried them by main strength towards the baggage waggons. They seemed as helpless as if they were dead.
