The medical examiner said there was no significant trauma to Brunn’s body.
A Georgia Department of Corrections spokesman said Brunn was found unresponsive in his cell at 4:15 p.m. Thursday. He was pronounced dead at a local hospital an hour later.
Brunn was charged with the Dec. 2 killing of Jorelys Rivera at the Canton apartment complex where she lived. On Tuesday, he pleaded guilty to various charges, including murder and child molestation, and was sentenced to life in prison without parole.
According the DOC, Brunn had been held at the Georgia Diagnostic and Classification Prison in Jackson since Tuesday evening, where he was interviewed by mental health staff on Wednesday.
The GBI is continuing to investigate the incident.