parshanut torah comment - Who killed Shaul?

Ⅰ Sh'muel 31:3–5:

וַתִּכְבַּד הַמִּלְחָמָה אֶל שָׁאוּל…. וַיֹּאמֶר שָׁאוּל לְנֹשֵׂא כֵלָיו שְׁלֹף חַרְבְּךָ וְדָקְרֵנִי בָהּ… וְלֹא אָבָה נֹשֵׂא כֵלָיו כִּי יָרֵא מְאֹד וַיִּקַּח שָׁאוּל אֶת הַחֶרֶב וַיִּפֹּל עָלֶיהָ. וַיַּרְא נֹשֵׂא כֵלָיו כִּי מֵת שָׁאוּל וַיִּפֹּל גַּם הוּא עַל חַרְבּוֹ וַיָּמָת עִמּוֹ.‏

As literal a translation as feasible:

The battle was heavy against Shaul…. Shaul said to his arms-bearer "unsheathe your sword and pierce me with it…"; and his arms-bearer did not wish to, for he is much afraid. Shaul took the sword and fell upon it. His arms-bearer saw that Shaul dies, and he fell, he too, on his sword and died with him.

In Ⅱ Sh'muel 1, someone comes to David with news. He tells him (in verses 6–10):

נִקְרֹא נִקְרֵיתִי בְּהַר הַגִּלְבֹּעַ וְהִנֵּה שָׁאוּל נִשְׁעָן עַל חֲנִיתוֹ…. וַיֹּאמֶר אֵלַי עֲמָד נָא עָלַי וּמֹתְתֵנִי כִּי אֲחָזַנִי הַשָּׁבָץ כִּי כָל עוֹד נַפְשִׁי בִּי. וָאֶעֱמֹד עָלָיו וַאֲמֹתְתֵהוּ כִּי יָדַעְתִּי כִּי לֹא יִחְיֶה אַחֲרֵי נִפְלוֹ….‏

As literal a translation as feasible:

I happened upon the Gilboa Mountain and, lo, Shaul leaned on his spear…. He said to me, "stand, please, over me and kill me, for the tremor has grabbed me, for all yet my soul in me". I stood over him and killed him, for I knew that he will not live after his falling….

Who killed Shaul? Was the reporter simply lying?

Answer

Radak explains "His arms-bearer saw that Shaul dies" with

i.e., close to death… but he did not die yet until the [reporter] killed him….

Alternatively, Radak continues,

it's possible the [reporter] lied: he didn't kill him but found him dead after [Shaul] had fallen on his sword. He said [he'd killed Shaul] to appeal to David….

Ralbag (Ⅰ Sh'muel 31:4 and Ⅱ Sh'muel 1:6) offers the latter explanation also, but prefers the former, which he fleshes out:

Shaul did not die in falling on his sword, and this [reporter] finished the job, killing him.… "And lo, Shaul leaned on his spear" seems to mean that after he fell on his spear and saw that it didn't pierce him, Shaul leaned on it forcefully to complete the piercing; when he saw he couldn't do it, he then asked the [reporter] to kill him.

(Abarbanel (to Ⅱ Sh'muel 1:9) says similar to the last.)