Meltdown alert! Selena Gomez didn't have the best night at KIIS FM's 2013 Jingle Ball. The 21-year-old star got held up during her performance on stage when her audio and mic malfunctioned. Her reaction? The "Slow Down" singer dropped the f-bomb and later walked off stage before finishing her set. See more pics of Selena here.

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"Sorry, the sound isn't working!" Gomez was heard yelled to the crowd. "Are you guys having a good night? I promise, a lot cooler people are gonna come out tonight," Gomez continued. "Is it okay if I perform two more songs and you guys can get to it?"

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But it didn't get any better. Clearly agitated, Gomez continued to speak to the crowd hoping the issue would quickly be resolved. "I have to thank you guys so much for allowing me to be able to perform the music that I love," Gomez said. "And I have to say that before you guys go on to the people that you care about, I really appreciate you supporting everything that I do. So this next song is the first song I had hit No. 1, and it's called 'Come & Get It.'"

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After the song, Justin Bieber's ex decided to leave the stage instead of finishing her set -- to a crowd filled with mostly children. "She was pissed doing the next song and she said two more songs," an eyewitness tells Us Weekly. "[She] didn't do the last one."

This article originally appeared on Usmagazine.com: Selena Gomez Curses During Jingle Ball 2013 Performance, Walks Off Stage