Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[176] When they had done as they were commanded, the rest of his brethren were astonished and disturbed, and were afraid for themselves, so they immediately got on horseback, and rode away to their father; but somebody there was who prevented them, and told their father they were all slain by Absalom; whereupon he was overcome with sorrow, as for so many of his sons that were destroyed at once, and that by their brother also; and by this consideration, that it was their brother that appeared to have slain them, he aggravated his sorrow for them. So he neither inquired what was the cause of this slaughter, nor staid to hear any thing else, which yet it was but reasonable to have done, when so very great, and by that greatness so incredible, a misfortune was related to him: he rent his clothes and threw himself upon the ground, and there lay lamenting the loss of all his sons, both those who, as he was informed, were slain, and of him who slew them. But Jonadab, the son of his brother Shemeah, entreated him not to indulge his sorrow so far, for as to the rest of his sons he did not believe that they were slain, for he found no cause for such a suspicion; but he said it might deserve inquiry as to Amnon, for it was not unlikely that Absalom might venture to kill him on account of the injury he had offered to Tamar. In the mean time, a great noise of horses, and a tumult of some people that were coming, turned their attention to them; they were the king's sons, who were fled away from the feast. So their father met them as they were in their grief, and he himself grieved with them; but it was more than he expected to see those his sons again, whom he had a little before heard to have perished. However, their were tears on both sides; they lamenting their brother who was killed, and the king lamenting his son, who was killed also; but Absalom fled to Geshur, to his grandfather by his mother's side, who was king of that country, and he remained with him three whole years.