For the third time this week, murder charges have been filed in the death of a child in Gwinnett County.

Rodney Hamilton has been charged with murder and cruelty to children in the death of his 3-year-old niece Tamiah Hamilton, whom he had adopted.

Gwinnett Police Cpl. Deon Washington says the child was brought to the hospital with a head injury on Jan. 30 and died four days later.

Recently released autopsy results reveal she died of blunt-force trauma to the head.

“The doctor is not able to determine exactly what the mechanism was, but she does believe it was caused at the hands of another person,” he tells WSB’s Sandra Parrish.

Washington says when interviewed by police, Hamilton couldn’t provide any answers as to how the child was injured.

He becomes the fourth person charged with murder this week involving three children.

The parents of a 10-week-old baby were arrested after the emaciated child died this week.  Duluth Police say Herbert Landell and Lauren Fristed fed the baby girl watered-down breast milk.

Former Buford High School and SEC football standout Steven Singleton was also charged this week with the murder of his girlfriend’s 4-year-old son.