How might this account of a murdered chief judge be considered evidence of the truthfulness of the Book of Mormon?

Immediately after the discovery of the murdered chief judge, “a public proclamation was then sent out by heralds announcing the murder and calling a day of fasting, mourning, and burial (see Helaman 9:10). The day after the death of a political leader was traditionally a day of fasting, mourning, and burial (see 1 Samuel 31:13; 2 Samuel 1:12)” (Welch, “Case of an Unobserved Murder,” 242).