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Christina McClarty's exclusive interview with Justin Bieber turned emotional when the pop star reflected on the recent loss of a 6-year-old fan, who referred to herself as Mrs. Bieber.

VIDEO: Justin Bieber Spills Tour Secrets

Bieber called Avalanna Routh his "angel" and even appeared with her on the Today show. Last week, cancer took Avalanna's life -- a point that Bieber found difficult to discuss.

In the interview, Bieber was at a loss for words in describing their relationship, but at the opening show of his Believe Tour, he dedicated a song to the little girl and later tweeted, "Goodnight Avalanna. Tonight was for you. I love you."

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Watch the video for more and tune in to ET tomorrow to see how Bieber surprised a group of unsuspecting fans.