Valmiki Ramayana Yuddha Kanda Sarga 93 Shloka 34

पुत्रवधसन्तप्तः very sad about the death of son, क्रूरः cruel, सःरावणः that Ravana, क्रोधवशम् overpowered by anger, गतः went, बुद्ध्या to destroy, समीक्ष्य thinking, सीताम् Sita, हन्तुम् will kill, व्यवस्यत deciding

Feeling very sad about the death of his son, cruel Ravana overpowered by anger went thinking to destroy Sita.