According to authorities, Theodore "Ted" Cornell Lockett, 21, returned late Saturday to his grandmother's Apache Trail home, where he had lived for six months before Lockwood asked him to move out.
Around 10 p.m., Lockett confronted his grandmother in the living room and began assaulting her, knocking her to the ground and striking her several times in the head with a glass table, a report from Richmond County sheriff's Sgt. Daniel C. Carrier said.
Lockett then called his mother, Sondra Lockett, and told her he'd just killed his grandmother and was going to kill her, the report said.
Theodore Lockett "then went back inside the residence and assaulted Lockwood again" by striking her in the head several times with a microwave oven, the report said.
When law enforcement arrived, they found Lockett inside and he surrendered without incident, Carrier said. His mother had contacted them after her son called, he said.
Also inside the house but unharmed was another woman, a bedridden relative for whom Lockwood was caring, Carrier said.
Authorities aren't sure what might have sent Lockett, who has no apparent criminal record, into a rage. He has been treated at a behavioral health facility but has no known psychiatric diagnosis, Carrier said.
Lockett was booked into the Richmond County jail at 2:15 a.m. Sunday on charges of aggravated assault, burglary and making terroristic threats.
The charge of murder was added when his grandmother died about 5 a.m. Sunday at Medical College of Georgia Hospital.