McManaman said she used to bring her kids out to the lake to skip rocks. She said she had no idea that the answer and the clues to her grandfather's disappearance may have been just feet away underwater.
In fact, over the years, when she and her kids drove by the lake, they wondered aloud if grandpa was in the lake, she said. "Maybe that's where he's at," she said.
The year he disappeared had a lot of rain, perhaps allowing a deeper lake to hide its secrets better, she said.
Authorities didn't know what they had until Tuesday, when they sent down Darrell Splawn, a diver with the Highway Patrol's underwater search and recovery team.
And even then, it was tough to know anything for certain. Visibility is only about 4 inches at the bottom of the lake. There's lots of murky muck to sift through.
"You can't see anything," Splawn said. "You basically just go down there and feel with your hands. It's just a blind feel."
Still, he found a shoe, so they attached a tow cable and pulled the cars out.
"It didn't really cross my mind as to a body being in it," Splawn said. "It could have been a shoe, but whenever we brought them up to the shore ... you could see the skeletal remains in them."
A second search by the diver found a skull and a few other bones.
Positive identification of the bodies could take years, authorities warn. They'll try to match DNA evidence if possible. The DNA testing will take place at the University of North Texas Health Science Center, which already has DNA samples from Duncan's relatives, said spokesman J. Todd Matthews.
A muddy wallet and purse could hold some clues.
While the scientists look for answers, the troopers hope they've provided some peace of mind.
"We are very fortunate to get to help these people and give their family closure, for they have lost loved ones," said Trooper Hoyle, who talked to the brother of one person missing for more than four decades.
"They didn't know that they were kidnapped or how they'd become missing, but I do believe that we gave them some closure ... so that they can have some resolve and serenity in their own lives."