She almost gave him a HEA-AH-AH-ART ATTACK!

Demi Lovato teamed up with Sydney, Australia's KIIS 1065 to give one of her biggest fans the surprise of a lifetime. The fan, Nathan, believed he was recording a video to be played for Demi during a radio interview the next day.

He had some pretty sweet things to say about how the 22-year-old singer made him a better person, and changed his life for the better.

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He also pretty adorably geeked out about finally getting to see his favorite singer in concert after waiting seven years. "Demi, you are just one of the strongest people I know and I cannot thank you enough for what you’ve done for everyone, for me," Nathan says in between hyperventilating.

His reaction when she walks out ENDS US.

After he collected himself, they hugged it out, and it was beautiful.

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Watch the whole video here.

We mean...

Demi Lovato's changing lives around the world, everybody. Watch this 5-year-old propose to her below.