Bhagvan Sri Ram, Mata Sita and Lakshman were residing in the Chitrakuta Mountain during their exile period in the Ramayana. Kakasura, son of Indra, in the form a crow was flying over the Chitrakuta and noticed the divine couple.
Sri Ram was lying on the lap of Mata Sita and sleeping. Kakasura came in the form crow and scratched Mata Sita. The painful cry of Sita woke up Sri Ram.
Bhagavan Sri Ram immediately realized that the crow was Kakasura. He took up a sharp blade of grass, infused into it the spell of Brahma and directed it at the crow.
Fearing for his life, Kakasura flew all over the world. But the divine arrow followed him.
Trimurtis, Devas and Saints could not save Kakasura. Finally, Kakasura took refuge at the feet of Sri Ram.
Bhagvan Sri Ram said that the Brahmastra could never become futile so the arrow will hit the right eye of Kakasura. Accordingly, the arrow struck the right of eye of Kakasura.