Seven-week-old Aniston had been missing since Jan. 9. Police said her body was found by a motorcyclist Sunday in a ditch along Singleton Parkway. WMC-TV, Memphis, reported.
"I would say that it seems like the body has been there for some time," Millington Police Chief Rita Stanback said after the body was discovered.
"You know, this is a trying scene for everybody. I'm a grandmother myself and this is something that is very difficult to deal with."
The news website MemphisRap.com reported Leslie Balling, an attorney for the baby's mother, said Andrea Walker, 33, surrendered to authorities Monday morning and was charged with first-degree murder. Walker had earlier been charged with aggravated child abuse and child neglect after allegedly telling police Aniston had disappeared after she had left the infant and her 3-year-old child at home alone while she dropped off her 5-year-old son at school.
Ballin said Walker declined to talk to investigators Monday morning, WMC-TV said.
"At this time, she's not going to make that statement," Ballin said. "At the appropriate time, once our investigation has progressed some, she will decide at her trial or at any hearings in the future if it's appropriate for her to make a statement."
Memphis Police Director Toney Armstrong, in a statement Monday, called the case a difficult one emotionally.
"It is heartbreaking to confirm that an innocent child's life has been taken, but now family members of Aniston Walker can have closure and begin the healing process of losing a loved one," Armstrong said.
2014: The Year in Music [PHOTOS]