Willard Richards recalls that Joseph witnessed Hyrum's death, then fired into the hallway at martyrdom.
Willard Richards, "Two Minutes in Jail," in Manuscript History of the Church, volume F-1, August 1844, 184, The Joseph Smith Papers website, accessed August 11, 2021
As he struck the floor he exclaimed emphatically; “I’m a dead man.” Joseph looked towards him and responded, “O dear! Brother Hyrum!” and opening the door two or three inches with his left hand, discharged one barrel of a six shooter (pistol) at random in the entry from whence a ball grazed Hyrum’s breast, and entering his throat passed into his head, while other muskets were aimed at him, and some balls hit him.