चिन्तयमानस्य as he was thinking, तस्य his, पूर्वम् formerly, अनेन by such, शब्दवेधिना Capable of hitting the target by following the sound, अज्ञानात् without knowledge, यत् which, कृतम् has been committed, दुष्कृतम् sinful, कर्म act, प्रत्यभात् flashed back.

While he was thus reflecting on a sinful act he had inadvertently comitted long ago, the act of discharging an arrow that could hit its target following the sound, flashed in his mind.