Law enforcement sources tell TMZ ... Craig Raymond Turner died of a self-inflicted gunshot wound at his home in Studio City, CA. Authorities arrived at his place just after noon Tuesday and he was pronounced dead at the scene.

Craig was born when Tina was 18 ... before she married Ike Turner. Once Tina and Ike wed, Ike adopted Craig. His biological father was a saxophonist named Raymond Hill, who performed with Ike's band.

The sad news of his death comes as Tina is making a rare trip outside her new home country of Switzerland to attend Paris Fashion Week events.

Craig was in the real estate business in the San Fernando Valley. He was 59.