Falling to the earth in its earlier Book of Mormon manifestations has consistently been a response to a spiritual experience. (See commentary accompanying Mosiah 4:1.) In this case, it is not the murder per se, which would have been a grisly sight, that was a spiritual experience but the confirmation of Nephi’s prophethood. The terrible sight astonishes them as the Spirit witnesses that Nephi’s prophecy has been fulfilled to the letter.