A family member tells us CJ suffered an apparent heart attack Sunday night in Jasper, Alabama ... he was taken to a local hospital by ambulance, but didn't make it.

Fans of the show remember the Jasper native auditioning for the judges back in 2014 in Salt Lake City ... blowing them away with his version of Allman Brothers Band's "Soulshine."

Judge Keith Urban told CJ, "You sing 'cause you have to sing, not 'cause you want to sing. And, I mean that in the deepest way. And, that's why it's so believable and real."

Following his incredible audition, CJ rocked America with powerful versions of "Too Close," "American Woman," and "Free Fallin'." He was chosen by the judges as a wild card in the semi-finals after not receiving enough votes, getting kept in the competition -- making it all the way to the top 6 before getting eliminated.

After "Idol," CJ performed with Darius Rucker at The Grand Ole Opry, someone he's said was a massive influence on his style. He even played for audiences in the competition show's season 13 tour.

He was only 31.