"Elder Richards had not been injured in the attack. This miracle fulfilled a prophecy made a year earlier by Joseph Smith, who had told Elder Richards that there would be a time when “the balls [bullets] would fly around him like hail, and he should see his friends fall on the right and on the left,” but he would not be hurt. (History of the Church, 6:619).
There is no evidence that Joseph Smith ever gave Willard Richards such a promise . Richards didn't say it in any account of the assassination nor in any known talk, letter or writing. Joseph Smith's journal doesn't mention the story nor any account while Smith was alive.
The story was never told before Richards death in 1854. There seems to be an attempt to create fulfilled prophecies AFTER the FACT. So where did the "prophecy" come from?
http://www.116pages.com/2017/11/willard-richards-prophecy.html?m=1