Who was the "Na'ar"?
Rashi (citing Midrash Tanchumah): Some say that he was Moshe's son Gershom. 1
Oznayim la'Torah: He was a Shali'ach-Beis-Din
See Sifsei Chachamim. See also Oznayim la'Torah as to why it was probably Moshe's son.