Justin Bieber Surprises Selena Gomez, Concert Goers

Those in attendance at the Pacific Amphitheatre in Costa Mesa, California on Sunday night enjoyed more than a fun set by feature act Selena Gomez.

They were also treated to a surprise performance by Justin Bieber, who hit the stage, gave his girlfriend a hug and then launched in an acoustic rendition of "Cry Me a River.

Justin later Tweeted about the experience: "Had a greatnight and surprised the people. felt good to be on stage. nothing is changing that selenagomez u did great tonight. proud of u."