The mystery surrounding a DeKalb County grandmother’s whereabouts came to an end Thursday, three weeks after her grandson was found in her car.

Through dental records, investigators determined a body found near I-20 was that of Millicent Williams, DeKalb police said Thursday.

RELATED: Grandson charged with murder, though woman’s body not found

ALSO: Missing grandmother had previously feared for her life

Williams, 78, was reported missing July 27 from her Decatur-area home. Inside the Brookgreen Point home, there were signs of a struggle, including blood, and the woman’s car was missing. Later that day, Williams’ grandson was found in her car.

Gregory Williams, 36, was arrested July 27 in a Kroger parking lot and charged with kidnapping, aggravated assault and theft by taking. Two days later, he was charged with felony murder, though his grandmother’s body had not been located.

Investigators believe Gregory Williams attacked his grandmother with a knife and then disposed of her body with her car, according to arrest warrants. But Gregory Williams declined to tell police where he had taken the woman’s body, according to police.

Police and court records showed Millicent Williams previously feared her grandson would hurt her. Her grandson, an Army veteran with mental illness, had previously threatened to kill her, according to a police report.

Investigators used all-terrain vehicles, dogs and divers to search for Millicent Williams in a local park, pond and wooded areas. A tipster called police Wednesday to report a decomposed body down an embankment off I-20, about five miles from the woman’s home.

Credit: AJC

Police say Millicent Williams was killed by her grandson, who refuses to say where her body is.