Timeline of 2 Murders: How the Killings of Russell and Shirley Dermond Unfolded

The elderly Georgia couple was murdered four years ago and investigators still have no idea who is responsible.

The murders of Russell Dermond, 88, and his wife, Shirley, 87, have never been solved. Every resident in the exclusive, gated community where they lived has been interviewed. Every gardener, handyman and day laborer was checked out.

The couple's three grown children submitted to polygraphs and passed. The mystery that constitutes their killings has nearly driven Putnam County Sheriff Howard Sills mad. He's never before had a homicide case he couldn't solve. 

This is how the gruesome, heartbreaking murders of a genteel and well-liked retired couple unfolded.

May 2, 2014 Russell Dermond was seen walking the golf course near his home. It appears to be the last time he was seen publicly. A few days before, Shirley Dermond had played her regular, weekly bridge game.

May 3

The couple had accepted an invitation from their neighbors to attend a Kentucky Derby party in the pristine, wooded subdivision where they lived on the banks of Lake Oconee in Georgia. But the Dermonds never showed up.

May 6

After calling the couple for two days and getting no answer, the friends who hosted the Derby gathering came to the Dermonds' four-bedroom, well-appointed home and found the back door unlocked. The husband and wife called out to the Dermonds and walked into every room in the 4,255-square-foot estate. Nothing was out of place.

The garage was another matter. Behind the couple's Lexus SUV and their Lincoln Town Car, was Russell's body. His head was missing. Towels had been placed around the corpse to keep blood from draining under the garage door and onto the driveway. Shirley was nowhere to be found. 

The FBI was brought in. A reward was offered. Over the following week, Sills brought in cadaver dogs. He had divers drag the lake area behind the Dermonds' property. No trace of Shirley was found.

For the next 10 days, Sheriff Sills held press conferences and questioned the couple's three grown children and their neighbors.

He thought many things. Did Mrs. Dermond have something to do with what happened to her husband? Had she been kidnapped? Had she just run off? But her purse, her cellphone and her car keys were all inside her home. 

One of the couple's sons, Keith, told a reporter on May 14, "Each hour that goes by, my brother, my sister and me are becoming more resigned to the fact that we may never see her again and we may never know what happened.

"If she is still alive, we can't imagine what she is going through. The human spirit is incredibly strong, but it has almost got to the stage where we hope she is with out father, just to ease her suffering."

May 16

Two men out fishing six miles from the Dermond's home came upon a woman's body floating face-down. Her ankles were tethered to two 30-pound cinder blocks.

Sheriff Sills was summoned. He arrived by boat and personally pulled the body from the water. It was Shirley Dermond.

Decomposition and internal gases had swollen her 5 foot, 2 inch body to twice its normal weight. "She had been beaten to death," Sills told InsideEdition.com. "There were multiple blows to her head by some sort of blunt object, possibly a hammer."

Shirley's body was fully clothed. There were no signs of sexual assault. "Obviously, then, we did not look for Mrs. Dermond anymore," Sills said. "Up until that point in time, every electronic billboard in Georgia had her picture on it."

That was the last piece of substantial evidence to ever surface in the Dermond murders.

The sheriff has interviewed hundreds of people, he estimates. On a single day, coordinating with several law enforcement agencies, 250 people were questioned, he said. The couple's bank records have been reviewed. Their safety deposit box was opened. Their wills were scrutinized. Their phone records were examined, as were the tower cell phone records in the area. Their three children were separately given polygraph tests and passed. 

Russell Dermond's head has never been recovered. There were no unusual fingerprints or DNA evidence discovered in their home. No one saw the killer or killers. Shirley Dermond was a fastidious housewife and her home was spotless, Sills said.  

"It's unexplainable," Sills says of the case. "I've worked many homicides in my career and it really upsets me that we're not any better off today than we were four years ago."