Officials said Samantha Davis died around 12:30 a.m. at Novant Presbyterian Medical Center.
Davis, a senior from Union Pines High School, was competing in the Hare & Hounds Invitational on Saturday morning at McAlpine Park in Charlotte.
Officials said she suffered a seizure and went into cardiac arrest.
Davis also was a popular member of the high school band from Cameron, about two hours east of Charlotte.
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"She never put herself before anyone. She always had a smile on her face," friend Victoria Campbell told WSOC-TV. "If something was bothering you and she knew about it, she was right there to give you a hug and give you all of her support and cheer you up. She was smart and beautiful, inside and out."
Campbell said a softball injury led to an epilepsy diagnosis for Davis and that her parents said she became a tissue donor after she was removed from life support Sunday morning.