Updated story, May 10: EATONTON, Ga. (AP) — Law officers are planning to display the photo of 87-year-old Shirley Dermond, who they fear has been abducted, on digital billboards across Georgia in hopes of generating new leads on her disappearance.

Her husband, 88-year-old Russell Dermond, was found beheaded Tuesday at the couple's home in an exclusive gated community on the shores of Lake Oconee.

Putnam County Sheriff Howard Sills tells The Associated Press that the billboard messages are expected to be up and running this weekend.

The Federal Bureau of Investigation is helping to carry out the effort. Billboards around the state will have information so people can call in tips about her disappearance, Sills said.

Sills also said investigators have spoken with agents in the FBI's behavioral unit in hopes of gleaning insight about who might be responsible for the crimes.

"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 that 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 all left behind, making it difficult for investigators to attempt to track her whereabouts.

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.

Original story: EATONTON, Ga. (AP) — An elderly man was beheaded and found in his home, officials in a small central Georgia town said as authorities on Thursday sought help from the FBI in searching for his wife, whom they fear was abducted.

Friends found the body of 88-year-old Russell Dermond on Tuesday in the garage of the couple's home on the shore of Lake Oconee, Sheriff Howard Sills told WSB-TV (http://bit.ly/1mFkSus). His wife, 87-year-old Shirley Dermond, was still missing Tuesday, officials told the TV station.

The man had been decapitated, county coroner Gary McElhenney told WMAZ-TV (http://on.wmaz.com/1jCiqBa). Authorities said they believe the attack happened sometime between Friday and Sunday.

Putnam County Sheriff Howard Sills said he doesn't believe the attack was random, partly because there was no evidence of forced entry or a struggle.

Sills said Shirley Dermond's wallet, cellphone, purse and car were all left behind, making it difficult to track her whereabouts.

"There is nothing out of place. Everything is immaculate," Stills told The Telegraph newspaper of Macon (http://bit.ly/1fYy0rZ). "This is the cleanest house I've ever been in."

The community is guarded by a gate and security officers, and Sills said authorities are investigating whether the attacker may have approached the couple's home by boat.

"This is a huge lake, it spans four counties and entry could've been made by the lake," Sills said.

Surveillance cameras in the community were not working, Sills told The Telegraph.

Crews have searched part of the lake with sonar devices but haven't found anything, the sheriff said.

"This absolutely makes no sense at all," the couple's son, Bradley Dermond, told WMAZ. "We're still hoping that our mother is OK."

Shirley Dermond is described as 5 feet 2 inches tall and 148 pounds. She has gray hair and blue eyes. She is not considered a suspect in her husband's death, Sills said.

"We still approach this as if she's been abducted and we pray that she is alive, but we don't know anything about where Ms. Dermond is," Sills said.