ATLANTA (AP) — Authorities say a decomposing body found along a busy interstate has been identified as a grandmother who disappeared weeks ago.

DeKalb County police told local news outlets on Thursday that 78-year-old Millicent Williams was identified through dental records. She was reported missing July 27.

Police spokeswoman Shiera Campbell says police found the body Wednesday evening down an embankment off westbound I-20 in Atlanta after receiving a tip. She says the body was so badly decomposed that investigators couldn't tell if it was a man or woman.

According to arrest warrants, investigators believe Millicent Williams' grandson, 36-year-old Gregory Williams, attacked his grandmother with a knife and then disposed of her body. Gregory Williams was arrested July 27 and faces several charges, including felony murder. It's unclear if he has an attorney.