Doctors at the Wayne Memorial Hospital emergency room notified authorities of the death of Kamari Bryant on October 25.
Officials said the boy's mother - Donnisha Bryant - brought the child to the ER because he was non-responsive.
Detectives said an autopsy by the Greenville Medical Examiner's Office shows the child died of a trauma to his body.
Now, Bryant's boyfriend - 37-year-old Keefe Decarlos McPhail - is charged with one count of murder.
"No matter what the outcome of the investigation, this is still a terrible tragedy. It is not only emotional and stressful to the family members, but it was also stressful and emotional to the detectives working this type of case. I appreciate everyone - officers and citizens - that assisted in this investigation," said Sheriff C. A. Winders in a statement.
McPhail is in the Wayne County Detention Center without bond.