Valmiki Ramayana Aranya Kanda Sarga 44 Shloka 15

आशनिसन्निभः like thunderbolt, शरोत्तमः the great arrow, मृगरूपस्य assuming deer form, शरीरम् body, विनिर्भिद्य pierced, मारीचस्य Maricha's, हृदयमेव heart, बिभेद tore.

The great arrow which was like a thunderbolt first pierced into the body of Maricha who had assumed the form of a deer and then tore his heart.