What does a Grammy-nominated singer do if he happens to be shopping at the mall and hears a fan singing his song? He joins her, of course.

Ed Sheeran surprised a fan Sunday at West Edmonton Mall in Edmonton, capital of the Canadian province of Alberta. A video that appears to have been filmed by a friend of Sheeran's or a member of his crew shows the singer walking through the mall and up onto a stage where a young girl is singing his hit "Thinking Out Loud."

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Despite the fan's obvious shock, she manages to finish the song as a duet with Sheeran himself. The video has more than 2.7 million views on YouTube.

WATCHSheeran surprises fan singing his song at mall

According to the Edmonton Journal, Sydney Bourbeau, 13, was performing the song as part of a humane society fundraiser for her music school. She later told the local news outlet she thought someone was coming onstage to fix her microphone -- until the crowd began cheering.

"'I was like, should I stop?' I didn't want to stop, but I wanted to talk to him," Bourbeau told the Edmonton Journal. "This is, like, the best thing that's ever happened to me."

Bourbeau, who added she's been a fan of Sheeran's since his 2011 debut album, said later that day his manager texted her offering two tickets to his concert in town that night. The president of the music school hosting the fundraiser told the Edmonton Journal they didn't know Sheeran was at the mall, nor did they plan their event around his concert Sunday.

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Jake Roche, lead singer of the band Rixton, which is opening for Sheeran on his current tour, tweeted a short video of the duet Sunday, writing, "Went shopping with @edsheeran ! Heard a girl in the mall singing his song. He jumped up and surprised her. Amazing."