'American Idol' Alum C.J. Harris' Cause of Death Revealed as Heart Attack

American Idol alum C.J. Harris' cause of death has been revealed.

The musician — who finished sixth on the show's 13th season in 2014 — died of a heart attack on Sunday, a spokesperson for the Walker County Coroner confirms to PEOPLE.

Harris was rushed to the hospital in Jasper, Alabama, where CPR efforts were unsuccessful. He was 31.

During his time on the show, Harris won over judges Keith Urban, Jennifer Lopez and Harry Connick Jr. at his Salt Lake City audition. He sang the Allman Brothers' "Soulshine," earned a trip to Hollywood, and continued on the show with performances of Tom Petty and the Heartbreakers' "Free Fallin'," "Invisible" by Hunter Hayes, "Can't You See" by The Marshall Tucker Band and "If It Hadn't Been for Love" by The SteelDrivers.

"C.J. Harris was an incredible talent, and the news of his passing deeply saddens us. He will be truly missed," American Idol said in a statement on social media.

RELATED: 'American Idol' Alum C.J. Harris Dead at 31

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After the show, the musician performed at the Grand Ole Opry with Darius Rucker, released the single "In Love" in 2019, and later promoted his music across social media, updating fans regularly on Facebook with his release and touring schedules.

"I was always on the internet, trying to find a break, looking for which producers I could send my stuff to. I searched for American Idol and I saw they were doing the bus tour and they were going to be 30 minutes down the road from me," he told The Hollywood Reporter in 2014, adding that he previously tried out for Idol, The X-Factor and The Voice. "I said, 'You know what? I'm going to give it another chance. I've gotten so much better, my voice has matured and my playing has gotten so much better."

FOX Image Collection via Getty

Harris' love of music began as a child, he told the outlet, adding that his mother would sing to him over the phone while she was in prison. "Tears would just flow out of my eyes," he said. "When I was a little older, my granddad gave me a guitar. He had one in the shed and it had three strings on it. He said I didn't need to buy a whole new set of strings. So I would tune it in a way that when I strummed it, it sounded like it's in a key of whatever."

"I find different sounds. I just love music so I really try to find a sound that I really like and just play it," Harris continued. "I know that's weird, but that's what I do."

The musician teased "new music coming soon" in his final Facebook post before his death, wishing his followers a happy new year.

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Jessica Meuse, fellow American Idol season 13 finalist, paid tribute to her late friend on Instagram, writing that his "talent and smile will be missed."

"And the world is definitely a darker and eerily quieter place without you in it," she wrote. "I'll miss your random phone calls asking for life advice and talking about the music world... There are a lot of things I realize I will never understand — you leaving us so soon is one of those things."

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Season 13 winner Caleb Johnson also shared his thoughts about Harris' death, writing on Instagram that the news "hurts so much" and reflecting on their time as roommates during Hollywood week. Johnson posted a string of photos to go along with his tribute, including some from their Idol days, and hanging out by tour busses.

"We instantly became friends and formed a brotherhood pack with @realalexpreston @samwoolfmusic," he shared. "So many amazing memories and experiences with you CJ! Life is so fragile! I am so grateful that our lives got to cross paths in this lifetime. You were a beautiful, kind soul that always made the room brighter with your smile and laughter. Love you brother❤️❤️ you were taken from us way to soon! Until we meet again RIP ❤️⚡️"