Georgia Mysteries | The Dermond double murder

PUTNAM COUNTY, Ga. -- It was a crime so brutal, so shocking...so unexpected. An elderly couple murdered in their waterfront home in the Lake Oconee community.

Shirley Dermond was found weighted down beneath the water, while her husband, Russell, was found decapitated.

"Why do you take somebody's head off?" Jacksonville State University professor and former death investigator Joseph Scott Morgan asked. "What are you trying to do? Send somebody a message to peripherals to friends or associates? This is a warning or is this someone who is a raving psychotic?"

It's a gruesome crime scene, but one that could lead to an answer.

"I'm not going to tell you we don't have forensic evidence, because we do," Putnam County Sheriff Howard Sills said.

The only way forensic evidence can make a difference is if it is matched to a suspect...and so far, there is only one.

"We have a witness who saw a man in the yard on the day we believe the murder occurred," Sills said.

That man however has not yet been identified. At this point in the investigation, several questions continue to drive the mystery in such as how did the killer gain access to the home?

"They had a big lake view from the porches," Charles Mittelstadt said. "A tremendous property with a tremendous access to the lake."

In front of the home, a dock for a boat provided access without going passed gated security or surveillance cameras.

"I believe there is a water vessel involved in this," Morgan said. "I believe it's the only way you could facilitate this thing." 

But the biggest question remaining is why kill this elderly couple? 

"Unless there is some animosity by somebody here we don't know about and they were targeted for something that happened in the past," Sills said. "It has to be some sort of a robbery or robbery slash extortion."

If this theory holds, nothing has yet been uncovered to figure out the exact nature of this extortion plot. With this mystery being so violent and so brutal, until these questions are answered, and this mystery solved, the community along Lake Oconee remains at risk.

"Whoever did this is still out there," Sills said. "And they'll damn sure do it again."

PHOTOS | Home of Putnam County murder-kidnapping case