In the call to emergency dispatchers early Aug. 29, Heinze said he'd come home to find the bodies and that it appeared the victims had been beaten to death. Seven were found dead at the scene, an eighth died at a hospital, and the attack's only survivor remained hospitalized after being critically injured.
Police haven't released causes of death for the victims.
Hours after the bodies were found, Heinze was charged with evidence tampering, lying to police and drug possession. But police didn't say until Friday that they suspected him of the killings.
He had been briefly released on bond related to the lesser charges and arrested again later Friday. He was being held at the county detention center.
"It's my understanding that there was physical and testimonial evidence," said Glynn County police spokeswoman Candice Temple, who declined further comment. Authorities were holding a news conference later Friday night.
The dead included the suspect's father, Guy Heinze Sr., 45; his uncle, Rusty Toler Sr., 44; and his aunt Brenda Gail Falagan, 49. Also slain were Toler Sr.'s four children - Chrissy Toler, 22; Russell D. Toler Jr., 20; Michael Toler, 19; and Michelle Toler, 15.
Chrissy Toler's boyfriend, Joseph L. West, 30, was also killed. A phone message left for Heinze Jr.'s attorney, Ron Harrison, was not immediately returned.
Clint Rowe, who has been acting as a spokesman for the family, said he learned of the arrests while at a public visitation for the victims, saying it was "definitely a surprise."
"I'm floored right now," Rowe, who is an uncle to the Toler children, said from the funeral home. "But right now it's just an arrest. We have to see where this thing takes us so I'm going to keep my mouth shut until the Glynn County Police Department informs us of more."
The manager of the New Hope Plantation mobile home park where the slayings occurred said the arrest still leaves a lot of questions unanswered.
"I'm feeling just like everyone else is right now, we're all shocked," said Gail Montgomery. "We don't know what any of the circumstances are. We don't know if there was more than one or if it was him by himself." ---
Associated Press Writer Desiree Hunter in Montgomery, Ala., contributed to this report.