Mbh 1.2.19a

“Then shall I describe the Parva called Sauptika of frightful incidents. On the Pandavas having gone away, the mighty charioteers, Kritavarman, Kripa, and the son of Drona, came to the field of battle in the evening and there saw king Duryodhana lying on the ground, his thighs broken, and himself covered with blood. Then the great charioteer, the son of Drona, of terrible wrath, vowed, ‘without killing all the Panchalas including Drishtadyumna, and the Pandavas also with all their allies, I will not take off armour.’ Having spoken those words, the three warriors leaving Duryodhana’s side entered the great forest just as the sun was setting. While sitting under a large banian tree in the night, they saw an owl killing numerous crows one after another. At the sight of this, Aswatthaman, his heart full of rage at the thought of his father’s fate, resolved to slay the slumbering Panchalas. And wending to the gate of the camp, he saw there a Rakshasa of frightful visage, his head reaching to the very heavens, guarding the entrance. And seeing that Rakshasa obstructing all his weapons, the son of Drona speedily pacified by worship the three-eyed Rudra. And then accompanied by Kritavarman and Kripa he slew all the sons of Draupadi, all the Panchalas with Dhrishtadyumna and others, together with their relatives, slumbering unsuspectingly in the night. All perished on that fatal night except the five Pandavas and the great warrior Satyaki. Those escaped owing to Krishna’s counsels, then the charioteer of Dhrishtadyumna brought to the Pandavas intelligence of the slaughter of the slumbering Panchalas by the son of Drona. Then Draupadi distressed at the death of her sons and brothers and father sat before her lords resolved to kill herself by fasting. Then Bhima of terrible prowess, moved by the words of Draupadi, resolved, to please her; and speedily taking up his mace followed in wrath the son of his preceptor in arms.