The mule walked out from under him. He stayed in the tree.
וַיִּקָּרֵא אַבְשָׁלוֹם לִפְנֵי עַבְדֵי דָוִד וְאַבְשָׁלוֹם רֹכֵב עַל הַפֶּרֶד וַיָּבֹא הַפֶּרֶד תַּחַת שׂוֹבֶךְ הָאֵלָה הַגְּדוֹלָה וַיֶּחֱזַק רֹאשׁוֹ בָאֵלָה וַיֻּתַּן בֵּין הַשָּׁמַיִם וּבֵין הָאָרֶץ וְהַפֶּרֶד אֲשֶׁר תַּחְתָּיו עָבָר׃
שמואל ב יח:ט
"And Avshalom happened to meet the servants of Dovid, and Avshalom was riding on the mule, and the mule came under the thick boughs of the great terebinth, and his head caught in the terebinth, and he was left hanging between the heavens and the earth, and the mule that was under him went on."
Shmuel Beis 18:9
Yoav took three shafts in his hand and did not wait.
וַיֹּאמֶר יוֹאָב לֹא כֵן אֹחִילָה לְפָנֶיךָ וַיִּקַּח שְׁלֹשָׁה שְׁבָטִים בְּכַפּוֹ וַיִּתְקָעֵם בְּלֵב אַבְשָׁלוֹם עוֹדֶנּוּ חַי בְּלֵב הָאֵלָה׃
שמואל ב יח:יד
"And Yoav said, I will not wait like this before you. And he took three shafts in his hand and drove them into the heart of Avshalom, while he was still alive in the heart of the terebinth."
Shmuel Beis 18:14
They threw him into a pit in the forest and piled stones over him, and everyone went home.
וַיִּקְחוּ אֶת אַבְשָׁלוֹם וַיַּשְׁלִכוּ אֹתוֹ בַיַּעַר אֶל הַפַּחַת הַגָּדוֹל וַיַּצִּבוּ עָלָיו גַּל אֲבָנִים גָּדוֹל מְאֹד וְכׇל יִשְׂרָאֵל נָסוּ אִישׁ לְאֹהָלָו׃
שמואל ב יח:יז
"And they took Avshalom and threw him into the great pit in the forest and set over him a very great heap of stones, and all Israel fled, each man to his tent."
Shmuel Beis 18:17
The king climbed the stairs alone, saying it over and over as he went.
וַיִּרְגַּז הַמֶּלֶךְ וַיַּעַל עַל עֲלִיַּת הַשַּׁעַר וַיֵּבְךְּ וְכֹה אָמַר בְּלֶכְתּוֹ בְּנִי אַבְשָׁלוֹם בְּנִי בְנִי אַבְשָׁלוֹם מִי יִתֵּן מוּתִי אֲנִי תַחְתֶּיךָ אַבְשָׁלוֹם בְּנִי בְנִי׃
שמואל ב יט:א
"And the king shook, and he went up to the chamber over the gate and wept, and this is what he said as he went: my son Avshalom, my son, my son Avshalom, who would give my death in place of yours, Avshalom my son, my son."
Shmuel Beis 19:1