Todd Kohlhepp, the man arrested after a woman was found "chained like a dog" on his property in South Carolina, has confessed to seven killings, a sheriff says.
Kohlhepp told police on Saturday that he was responsible for the deaths of four people in 2003.
He also showed law enforcement officers where he said he had buried two other victims on his property.
This comes after the discovery of a body at the 95-acre site on Friday.
Registered sex offender Kohlhepp, 45, has been charged with four counts of murder and one of kidnapping.
He was arrested on Thursday when police found a woman on his property chained in a container.
She had been missing, along with her boyfriend, since late August.
The woman was discovered after police heard banging noises and screams from inside a metal shipping container in Woodruff, 130km northwest of the state capital of Columbia.
It was described by Spartanburg County Sheriff Chuck Wright as "a hellish place to be locked in hot weather. No lights, no windows, no air flow".
Officers had been led to the property thanks to a tip-off by a sex-crime investigator.
The woman told officers that Kohlhepp had shot and killed her boyfriend in front of her.
Mr Wright confirmed on Saturday that the body found on the site a day earlier was that of her boyfriend Charles Carver, 32.
"They're obviously heartbroken," he said after talking to the Carver family. "It's terrible."
Mr Carver died of multiple gunshot wounds.
Kohlhepp told investigators that he was also the gunman behind the fatal shooting in 2003 of four people at a motorcycle shop in Chesnee near Spartanburg, South Carolina.