Alright, I checked several sources and was able to find info on this site, which in turn has as its source the book General Lee’s Immortals: The Battles and Campaigns of the Branch-Lane Brigade in the Army of Northern Virginia, 1861-1865, by Michael C. Hardy. Hardy has been recognized by the North Carolina Society of Historians and has published several articles and book about North Carolina during the Civil War. He has also received medals from the Sons of Confederate Veterans and the Daughters as well, which made me kind of... suspicious, you know? So I tracked down the book and checked it out and it seems to be well sourced, using mainly primary sources and adequate footnotes. This is of course no in-deep analysis, but it seems to signal that we can trust Hardy insofar as objective facts are concerned.

Let's start off by what's uncontested: how Jackson died. You are right that he died in a friendly fire incident. But it wasn't a single guy that shot him for accident, but a whole regiment, to be precise the 18th North Carolina. It happened at night during the Battle of Chancellorsville. This battle took place in the thicket of forests known as "The Wilderness", a rather dreary place where Grant and Lee would fight a nightmarish battle in 1864. In 1863, however, Lee was facing a much less capable adversary: "Fighting Joe" Hooker, who despite his nickname actually did very little fighting at Chancellorsville. This is often considered to be Lee's greatest victory, though I'd say that is as much owed to Hooker's poor generalship as to Lee's good choices. But I digress. The point is that Lee daringly divided his Army in the face of Hooker's numerical advantage, sending them through the trees to attack the Union troops. One of Lee's columns was naturally led by Jackson, which included the 18th North Carolina.

Fighting at night, in the middle of the woods, not completely sure of where the Yankees were, brought disaster to the Confederates when Jackson, together with other officers including A.P. Hill, decide to rode on ahead to reconnoiter the enemy and then returned to their command. But the nervous soldiers of the 18th North Carolina, believing them to be Yankee cavalry and unable to recognize their commanders in the moonlight, fired upon them. According to Hardy, Hill's staff was "decimated", Hill himself suffered minor damage, and Jackson's staff was almost unharmed. But Jackson was struck at least three times, two of them on his arm, which had to be amputated. But given the state of medicine in the 1860's, and especially the sorry state of the Confederate medical corps, Jackson was not able to recover. He soon got pneumonia and passed away.

So, there was no individual soldier that shot Jackson accidentally resulting in the General's inmediate death. Rather, a nervous regiment shot Jackson and several other officers accidentally, with Jackson dying of pneumonia eight days later. Given the technology of the war, at least three different soldiers must have fired those three different bullets that hit Jackson. But we'll never know which soldiers fired those three bullets, it's simply impossible. If the culpable was to be punished, then, it would have been either the entire regiment or its officers. In command of the 18th North Carolina that night was Colonel Purdie... who doesn't seem to have a name, or at least Hardy just calls him "Colonel Purdie". Anyway, Purdie was the one who ordered the men to "fix bayonets; load; prepare for action!" when they heard the sound of horses moving towards them. This was actually Jackson and his party. When the horses were spotted the men fired, not knowing it was their own side they were firing upon.

Hill then asked who commanded the regiment and upon learning it was Purdie, he chastised him for "firing at a noise". But Hardy relates then that "Sometime in next few hours, Hill sought out Purdie and publically apologized". Now, the 18th North Carolina was one of the regiments that formed the "Branch-Lane Brigade" under the command of Brigadier Generals Lawrence Branch and James H. Lane. Branch, the first commander, died at Antietam, so Lane was the one in overall command of the brigade that day. The Brigade was in turn part of A.P. Hill's Light Division in Jackson's Corps. Lane thus was blamed for the incident by some, one officer saying that "General Lane got scared" and "fired into our men". But Lane then claimed after the war that "In all my intercourse with Genl. A. P. Hill I never heard him, nor have I ever heard any one else censure the 18th regiment for firing under the circumstances". Hardy just notes that "the debate still continues", referring to the debate of who really was to blame.

What seems clear is that no one was punished. The regiment was deeply horrified at what it had done, but everyone recognized it as a terrible accident and, given the circumstances, it was decided not to punish the men. In fact, from the recollections and testimonies Hardy collects it seems that nobody even considered to punish the men and that they weren't afraid of anything like that either. The officers weren't punished either. Purdie was admonished by Hill but got an apology soon thereafter. Purdie then died in battle, but given that he was still fighting and due to Hill's apology, I think we can safely say that Purdie wasn't going to be punished. And despite those few pointed lines in official reports, no one punished Lane, who remained in command of his brigade. Altogether, no one in the 18th North Carolina suffered any consequence from the incident, unless the sorrow and regret they felt is considered.