His death was confirmed by family members on his Facebook page.
The gun was planned for use as a prop in an upcoming Carter video, according to WTVD-TV. It somehow went off in Carter's apartment, killing him.
The musician had recently signed with Triple Threat Management, which released a short statement on Carter's death, WTVD reported.
"Justin had a potential to, you know, in our eyes and a lot of people's eyes, to be the next Garth Brooks," the company’s Mark Atherton said.
Atherton told the news station that the gun that was supposed to be used in an upcoming music video is the same one that killed him. It’s still unclear exactly what happened and how the singer was shot.
Carter's mother, Cindy McClellan, told Fox News, "He was a wonderful artist."
“He was the voice. He was the total package and we’re trying to keep his legend (alive). ... He just loved music. He was very gifted, and by God, his voice was spectacular,” McClellan said.
Triple Threat said they still plan to release music that Carter had recorded, with the proceeds benefiting the family, according to WTVD.
A post on Carter’s Facebook page is asking for donations for the family to help cover his funeral costs.