He died on returning from Norway where he was introduced to world chess champion Magnus Carlsen.
http://en.chessbase.com/post/john-forbes-nash-1928-2015
In perhaps his last joke, he compared Carlsen to Justin Bieber:
"With a wry sense of humour Nash says: “There is a paradoxical resemblance between two persons: I didn’t expect to meet Justin Bieber!”