The suspect, Todd Kohlhepp, may be linked to as many as seven deaths, Spartanburg County Sheriff Chuck Wright said on Saturday.
Investigators have searched his property for more bodies after that of the kidnapped woman's boyfriend was found there in a shallow grave.
After being freed on Thursday, the woman told authorities she had witnessed Kohlhepp shoot her boyfriend.
The couple had been missing for two months.
Kohlhepp was denied bail on the quadruple homicide, the Spartanburg Herald-Journal reported from the courtroom at the county jail, which was filled with relatives of the victims and reporters, the newspaper said on its website.
A photograph showed Kohlhepp, 45, appearing before the judge in an orange jumpsuit.
Kohlhepp, a registered sex offender who works as a realtor, declined two opportunities to speak in front of the victims' families, the Herald-Journal reported.
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