There were no other apparent injuries to Jadon Higganbothan.
The medical examiner said Monday that a woman whose body was also found buried in the yard on Ashe Street was shot to death.
An autopsy showed 28-year-old Antoinetta McKoy has two gunshot wounds to the head.
Seven people have been charged with their murders, including the leader of the so-called Black Hebrews cult - 27-year-old Peter Moses - and Higganbothan's mother.
McKoy and Jadon Higganbothan were both last seen alive last year. The Ashe Street home is located a few miles from another home on Pear Tree Lane where McKoy and Higganbothan lived with the group.
ABC11 sources confirm the Ashe Street home was once the rental property of Moses' mother.