In this way the demon Pūtanā, very much aggrieved because her breast was being attacked by Kṛṣṇa, lost her life. O King Parīkṣit, opening her mouth wide and spreading her arms, legs and hair, she fell down in the pasturing ground in her original form as a Rākṣasī, as Vṛtrāsura had fallen when killed by the thunderbolt of Indra.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
निशाचरीत्थं व्यथितस्तना व्यसु- र्व्यादाय केशांश्चरणौ भुजावपि । प्रसार्य गोष्ठे निजरूपमास्थिता वज्राहतो वृत्र इवापतन्नृप
niśācarītthaṃ vyathitastanā vyasu- rvyādāya keśāṃścaraṇau bhujāvapi | prasārya goṣṭhe nijarūpamāsthitā vajrāhato vṛtra ivāpatannṛpa
SB 10.6.13