Her husband, 88-year-old Russell Dermond, was found beheaded Tuesday at their home in a gated community on Lake Oconee.
Putnam County Sheriff Howard Sills said the billboard messages are expected to be up this weekend. The Federal Bureau of Investigation is assisting.
The billboards will have information so people can call in tips about her disappearance, Sills said.
He said investigators have spoken with the FBI’s behavioral unit in hopes of gleaning insight about who might be responsible.
“We have no idea where Mrs. Dermond is and hope that she’s still alive,” Sills said.
Putnam County Deputy Coroner Marcus Turner said an autopsy showed Russell Dermond was already dead when his head was cut off, and authorities believe he died of a head or brain injury.
The couple’s lakefront home showed no signs of a struggle or forced entry and no ransom note was left behind. Shirley Dermond’s pocketbook, cellphone and car were left behind, making it difficult for investigators to attempt to track her. The neighborhood is guarded by security officers, but Sills said it’s possible the killer arrived by boat from the lake.
On Friday, Sills said he was plodding, trudging away” and still trying to identify people who might have been in the area when the couple was last seen.
The sheriff believes the couple was killed May 2 or May 3.