II Samuel 15:12

12 And Absalom sent for Ahithophel the Gilonite, David’s counsellor, from his city, even from Giloh, while he offered sacrifices. And the conspiracy was strong; for the people increased continually with Absalom.

II Samuel 17:23

23 And when Ahithophel saw that his counsel was not followed, he saddled his ass, and arose, and gat him home to his house, to his city, and put his household in order, and hanged himself, and died, and was buried in the sepulchre of his father.