Where can I find the story of Kaundinya's mountain retreat?

According to my understanding Koṇḍañña was the first to understand the Buddha's teaching and reach enlightenment at the Deer's Park . The senior monk was held in high-esteem, then he retired to the Himalayas in his last years. Where is the story of his retirement found? I already searched the wikipedia , but it seems controversial. Was he the same one as Vimalakoṇḍañña - born to King Bimbisāra (wiki makes a relationship but I am doubtful)?