Surviving participants attempted to describe in letters, diaries, and memoirs the hellish intensity of that day, many noting that it was beyond words. Or, as one put it: "Nothing can describe the confusion, the savage, blood-curdling yells, the murderous faces, the awful curses, and the grisly horror of the melee." Some men claimed to have fired as many as 400 rounds that day. May 12 was the most intensive day of fighting during the battle, with Union casualties of about 9,000, Confederate 8,000; the Confederate loss includes about 3,000 prisoners captured in the Mule Shoe.