Christopher and William Cormier, 31, were charged with murder Wednesday afternoon, according to Winder, Ga., police officer Chris Cooper. They'd previously been charged with concealing death.
It was not clear whether the brothers have an attorney.
Medical examiners declared the death a homicide based on the number and location of the man's injuries, Cooper said. The autopsy revealed that the man died of blunt force trauma to the head about a month ago.
Authorities still haven't definitively identified the body, Cooper said. But police in Winder and in Pensacola, Fla., have said they believe the remains are those of 30-year-old Sean Dugas of Pensacola, Fla., who had been reported missing.
Georgia authorities arrested the twins at a home being rented by their father.
Dugas was last heard from on Aug. 27, when he made plans to have lunch with a friend the next day, police said. When the friend went to pick him up for the meal, he wasn't home. After trying unsuccessfully for days to reach Dugas, the friend went back to his house on Sept. 7 to find it empty. Neighbors told her a U-Haul truck had been there Sept. 3 and they saw at least one man removing things.
That man told the neighbors that Dugas had been beaten and was going to live with him, police said.
The female friend continued to try to reach Dugas before calling police on Sept. 13.
Police in Pensacola identified a home in Winder and contacted police there. After visiting the home and talking to the twins' father, Winder police got a search warrant to investigate an area in the yard that appeared to have been recently disturbed. On Monday, they found a human body that had been encased in a plastic storage container filled with concrete.
Investigators have determined that Dugas knew the Cormiers, likely through a comic book shop in Florida because they were all involved in a trading card game, but police hadn't determined the extent of that friendship or how long it had been going on, Cooper said.