For several days, Edward Smith’s family had no idea where he was. But they had a feeling something was wrong.

And it was.

By the time the 78-year-old’s family reported him missing to police Sunday, Smith had been dead for four days, according to Cobb County police. And the last two to see Smith alive, his grandson and the grandson’s girlfriend, are now the two charged with his death.

Smith’s grandson, Casey Ryan Collins, 30, and Collins’ girlfriend, Sarah Elizabeth Cook, 23, both of Mableton, allegedly stabbed and strangled Smith to death inside the older man’s truck, according to arrest warrants obtained by The Atlanta Journal-Constitution. Then after killing him, Collins and Cook allegedly drove around town in the dead man’s white Ford pickup truck with his body still inside, the warrants state.

The duo later abandoned the truck, which was found Tuesday with Smith still inside, police said. On Wednesday, as Collins and Cook remained in the Cobb County jail facing homicide charges, family members struggled to make sense of a seemingly senseless crime.

“This is a nightmare. It’s a complete nightmare,” Smith’s daughter, Lisa Stitley, told The AJC by phone Wednesday night. “I can’t even begin to imagine. I keep thinking I’m going to wake up.”

Stitley said even though her father lived in Gwinnett County, he made the trip daily from his Lilburn home to see her and other family members in Cobb County. From there, Smith would sometimes make the trip to Villa Rica to see his 39-year-old girlfriend, Stitley said.

“He was very young at heart,” Stitley said. “And was in extremely good health for his age.”

Stitley last saw her father last Thursday morning, she said. From there, Smith planned to visit his grandson before driving to Villa Rica. But Smith never made it out of Cobb County. He had a cell phone, but it wasn’t working Thursday, possibly from a late payment, Stitley said.

Outside the Mableton home where Collins and Cook lived, the two allegedly assaulted Smith as he sat inside of his parked truck, warrants state.

“Cook stabbed Smith twice in the chest with a knife while Collins used a belt to choke Smith,” the warrants state. “After Smith was dead, Collins removed Smith’s wallet from Smith’s pocket.”

Then, investigators believe Collins and Cook drove around metro Atlanta and went shopping — all while Smith’s body was concealed in his truck, according to police.

For several days, Smith’s family worried endlessly about him. Collins and Cook played along, Collins’ mother told The AJC.

“They were upset,” Tammy Smith Connor said. “They acted just like they were worried just like we were.”

On Sunday, Stitley reported to Cobb police that her father was missing. Two days later, police made the gruesome discovery of the man’s body inside his truck left in south Cobb.

Cook has allegedly confessed to police what she and her boyfriend did, arrest warrants state. But Smith’s daughters said that other than stealing the older man’s money, they can’t imagine what motive the two would have had.

“My dad had been good to both of them,” Tammy Smith Connor said. “He always went the extra mile with family.”

Funeral arrangements for Smith have not yet been finalized.