The Herald-Journal of Spartanburg reports that, in an eight-page letter, Todd Kohlhepp wrote that he tried to tell investigators and informed the FBI, but he said "it was blown off."
He also wrote, "At this point, I really don't see reason to give numbers or locations."
Don Wood, chief division counsel with the FBI's Columbia office, said the agency has a pending investigation, but wouldn't comment specifically on what the FBI is doing.
The 46-year-old Kohlhepp pleaded guilty in May to seven counts of murder for killings that took place over more than a decade, all as he ran a real estate business. He was sentenced to life in prison.
His string of crimes was uncovered in 2016 after police rescued a woman chained at the neck in a storage container and investigators found a body buried in a shallow grave. The woman told investigators she saw Kohlhepp shoot and kill her boyfriend, who went with her for a cleaning job on the suspect's property.
SEE ALSO: Missing South Carolina woman found 'chained up like a dog' in container alive
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