"he had attained Nirvana"

Nirvāna (Sanskrit: निर्वाण) literally means "blowing out" — referring, to the supreme state freedom from suffering and the extinguishing of the fires of delusion and individualism.

Buddha's body after nirvana
Creative Commons Attribution Share AlikeBuddha's body after nirvana - Credit: Nimbu

In the Dhammapada, the Buddha says of nirvāna that it is "the highest happiness," "the unconditioned" (asankhata) mind, and is also known as "deathlessness" (Pali: amata or amāravati. Nirvana can be attained by anyone who leads a life of virtuous conduct and practice in accordance with the Noble Eightfold Path.