A 20-year-old man has been arrested in the fatal beating of his girlfriend's 4-year-old daughter while babysitting the child in Camden in July, officials say.

Najuquan Ross, 20, was charged Wednesday with one count of first-degree murder in the death of Natalise Gunter, according to authorities.

The child's mother, Lucy Gunter, was previously charged with endangering the welfare of a child for not calling for help until she found the child unresponsive three days after the alleged beating on July 15.

Authorities said Ross was watching the girl and two other children while Gunter was at work.

"When Gunter asked how her child was injured, Ross reportedly told his girlfriend that he had beaten her daughter for not wanting to eat dinner, and that she lost her tooth during the beating when she fell trying to fight back," the Camden County Prosecutor's Office said in a statement.

Ross is being held at Camden County Correctional Facility awaiting a detention hearing set for Tuesday.