Jamieson, Fausset and Brown on 2 Samuel 13:30-31

30-31. tidings came to David, saying, Absalom hath slain all the king's sons--It was natural that in the consternation and tumult caused by so atrocious a deed, an exaggerated report should reach the court, which was at once plunged into the depths of grief and despair. But the information of Jonadab, who seems to have been aware of the plan, and the arrival of the other princes, made known the real extent of the catastrophe.

2Sa 13:37-39. Absalom Flees to Talmai.