US authorities say a registered sex offender has confessed to seven killings, after a woman was found chained alive in a storage container.

Todd Kohlepp, 45, apparently told police that he was behind four deaths at a motorcycle shop in 2003 and also led authorities to the site of two more bodies on his South Carolina property.

This after another body was found at the site on Friday. That has been identified as the boyfriend of 30-year-old Kala Brown, who was inside the locked container – and is described as having been chained up at the neck, “like a dog.”

The couple went missing in August.

Brown is said to have told authorities that she saw Kohlepp shoot her partner.

The county sheriff says more bodies could be found.

Officials have also told the media that Brown and Kohlepp knew each other and that her abduction was not a random act.