Atlanta (CNN) -- [Breaking news alert, 7:23 p.m. ET]
"We now unfortunately know that Shirley Dermond was murdered," Putnam County, Georgia, Sheriff Howard Sills told reporters on Friday.
The body of the 87-year-old Dermond -- missing since her husband's decapitated body was found in their home two weeks ago -- was discovered in Lake Oconee, south of Athens, near a river channel, in 50-feet of water, he said.
"The head was not removed or anything like that," Sills said of Shirley Dermond's body.
A boat is believed to have been used in the abduction and killing of Dermond, Sills said.
Authorities were alerted by two fishermen who spotted something in the lake, he said.
[Original story published at 7:20 p.m.]
By any standard, the killings were grisly.
With the discovery of the body of an 87-year-old Georgia woman whose disappearance came to light after her husband's decapitated body was found in their home, authorities not only want to know who did it, but also why.
Shirley Dermond's body was found in the Oconee River, a close family friend told CNN on Friday.
"The whole family are in shock with the news of Shirley's body being found," said the Rev. David Key of Lake Oconee Community Church.
"We haven't even had a funeral for Russell because their kids wanted to wait. Now that we know about Shirley, we will start planning the funeral services for both."
From the beginning, investigators treated her disappearance as an abduction. Her purse, cell phone and car were all at the couple's million-dollar waterfront home on Lake Oconee where her husband's headless body was found.
Investigators believe she was taken from her home after her husband, 88-year-old Russell Dermond, was decapitated sometime between May 2 and May 4.
Russell Dermond's body was discovered in the couple's garage after friends, who hadn't heard from the couple in days, went to their home.
The FBI put up more than 100 billboards in its search for the missing woman, and it offered a reward of up to $20,000 for information to her location or the arrest of the person responsible for her disappearance.
In the days after Dermond's disappearance, authorities searched Lake Oconee in the vicinity of the couple's home -- turning up only a lawn chair and a Christmas tree -- and sent cadaver dogs into the nearby woods, to no avail, Putnam County Sheriff Howard Sills said this week. Police have also spoken to neighbors, family and friends.
So far, the investigation has turned up little to shed light on the crimes. Investigators aren't aware of any enemies the couple had made, or any reason someone would target them, Sills said.