The father, Frank Arthur Janssen, of Wake Forest, was rescued from an Atlanta apartment late Wednesday.
John Strong, FBI special agent in charge in North Carolina, says Janssen's kidnapping was related to his daughter's prosecution of North Carolina prisoner Kelvin Melton, who is serving a life sentence for his 2012 conviction for being a habitual felon. He was also convicted of assault with a deadly weapon with intent to kill.
Authorities say Janssen's kidnappers threatened to torture him and sent text messages to his wife making demands. They also sent her a picture of her husband tied up.
Authorities did not say what the demands were.