His sword: the pronoun his is ambiguous in Hebrew, meaning either Saul’s sword or the young man’s own sword (Good News Translation, New Century Version, Biblia Dios Habla Hoy, Nova Tradução na Linguagem de Hoje). The latter seems more likely.

Fell upon his sword: as in the case of Saul in the previous verse, this was an intentional act of suicide, so the translation should leave no doubt about this.

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 1. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .