Police Capt. Vincent Cannito said Friday that 51-year-old Clemens Fred Tinnemeyer of Las Vegas was a person of interest in the nationwide search for Cole.
Cannito says authorities think the grandfather was involved in drug dealing with Mexican nationals, and the boy's kidnapping was a "message."
Tinnemeyer was last seen in May and reported missing Sept. 11.
A nationwide Amber Alert remains in effect after two Hispanic men tied up Cole's mother and her boyfriend at their house Wednesday and abducted him.