Video: Justin Bieber sings Cry Me a River to Selena Gomez

Fans at Selena Gomez's show Sunday night at Pacific Amphitheatre Costa Mesa, California, undoubtedly spent the most amazing time of their lives.

For while Selena Gomez was on stage singing, her boyfriend Justin Bieber decided to surprise and presented without notice.

The artist of 17 years old, greeted his girlfriend with a hug before starting to sing 'Favorite Girl, and then interpret the tune of Justin Timberlake, Cry Me A River.