Arrest warrants showed each victim was beaten with a blunt object. None was shot, Glynn County police Capt. Jay Wiggins said.
Guy Heinze Jr., who cried "my whole family's dead" when he reported the slayings in a frantic 911 call Aug. 29, was charged Friday with eight counts of murder.
Clint Rowe, an uncle to four of the dead, said he found that hard to believe unless the victims were drugged, especially with several grown men among those killed.
"They would've fought until the end," Mr. Rowe said. "Wouldn't you think one person would've had a hard time killing eight people with a blunt object without someone giving them a fight?"
Hours after the slayings were discovered, police jailed Mr. Heinze on charges of drug possession, evidence tampering and lying to police. He was released on bond but charged with the killings nearly a week later.
His attorney, Ron Harrison, said Mr. Heinze was not involved in the slayings.
"He's upset and aggravated at being placed back in jail and is totally distraught over the whole situation," Mr. Harrison said.
Police have released few details about the brutal attack, including a possible motive, saying they don't want to reveal anything that could jeopardize the case.
The dead included the suspect's father, 45-year-old Guy Heinze Sr., and six members of an extended family the Heinzes lived with in a 980-square-foot mobile home just north of Brunswick.
Also killed were Rusty Toler Sr., 44; his sister Brenda Gail Falagan, 49; and Mr. Toler's four children: Chrissy, 22; Russell Jr., 20; Michael, 19; and Michelle, 15.
Chrissy Toler's boyfriend, 30-year-old Joseph L. West, was also killed. Her 3-year-old son, Byron Jimerson Jr., survived the attack with serious injuries, for which Mr. Heinze has been charged with attempted murder.
District Attorney Stephen Kelley said he won't make a decision on whether to seek the death penalty until after Mr. Heinze is indicted.