PORTO VELHO, BRAZIL – A 13-year-old girl is charged with murder after allegedly killing her pregnant sister and then cutting out her baby to give to another woman.

Police in Porto Velho, Brazil say the teen bludgeoned her 23-year-old sister, Fabiana Santana, to death on Oct. 18 with a metal pole, according to The Sun. The younger sister proceeded to open Santana's womb and take her unborn child.

When Santana's 7-year-old son witnessed the crime and attempted to protect his mother, the teen girl, who is the boy's aunt, drowned her nephew by throwing him into a lake and stoning him until his death.

Another family member found the bodies of Santana and her son two days later in a quarry.

Police say the teen killed her sister and took her baby on the orders of a woman who had been faking being pregnant and needed a baby so her boyfriend would marry her.

The older woman, Catia Rabelo, was arrested and confessed to inciting the teen girl and 15-year-old boy to commit the crime.

The girl allegedly went through with the murders as an act of vengeance.

"The girl made a separate claim that she committed the crimes out of revenge because she was sexually abused by her sister's husband and ill-treated by Fabiana who didn't believe her stories," said police chief Leisaloma Carvalho.

The baby is reported to be in good health in a local hospital.