You already seem to have the basic facts, so there isn't much more that I can add to it. Jackson himself was, as you note, struck three times, but he was not the only one hit by the men of the 18th Carolina. In Jackson's group, one man was killed and another wounded. Additionally, A.P. Hill and a small group of his men were close by, and caught in the same volley, resulting in nine more killed or wounded in the encounter overall. I'm unsure how many were hit multiple times, like Jackson, nor of course how of the soldiers many shot and missed, but it was a fairly large number of soldiers who were firing at targets which, obviously, they were not able to identify at the time of the shooting. It is extremely unlikely that anyone was certain of whom they had hit, and even less likely that they would have stepped forward to admit being the one who had shot their beloved commander. Having thumbed through several books which cover the death of Jackson, none even go so far as to name the officer who ordered the volley, let alone the rank-and-file who were involved. Best I can find for 'fault' is Brigadier General James Lane, who commanded the regiment, and would essentially assume de facto blame, as it likely isn't a coincidence that his career faltered and he would not see promotion for the rest of the war.