Police say the 18-year-old girl handed herself over at Manenberg Police Station after the incident at her home in Rio Grande Street during the early hours of Sunday.
According to the source the girl “snapped” after her uncle allegedly cut up her clothes during an argument and attacked her.
She had also reported his alleged abusive behaviour to police before.
“The uncle was abusive and she went to the police station to report him in the week,” says the source.
“On Sunday morning he was fighting with her and she stabbed him.”
Manenberg Police Station commander, Brigadier Enolium Joseph, says at 2am police were called to the girl’s home where they found her 29-year-old uncle with a single stab wound in the chest on the floor in the bedroom.
“He was allegedly aggressive and abusive towards the family.
“On Sunday it is alleged that he cut up her clothes during an argument and attacked her.
“She grabbed a kitchen knife and stabbed him in the chest. The 29-year-old male was declared dead on the scene. She fled the scene, but at 7.15am she handed herself over to police.
“Police are now investigating a murder case and the 18-year-old will appear in the Athlone Magistrate's Court.”