A 13-year-old girl allegedly killed her sister and cut out her unborn baby to give it to a woman, it is claimed.
The suspect also allegedly drowned and stoned her sister's seven-year-old son, Gustavo, to death when he tried to protect his mum.
She allegedly attacked her pregnant sister with an iron bar and a knife in Porto Velho, Brazil.
The teenager was arrested after Fabiana Sanatana's body was discovered in a shallow grave on October 21.
Her nephew's body was reportedly left in a reservoir less than 100 metres from where his mum was buried.
Police chief Leisaloma Carvalho said: “This is a crime that has the most seasoned police officers because there is evidence it was premeditated.
“The teenage suspect has admitted to killing her and her seven-year-old nephew.
"And told us that she threw Gustavo, who couldn’t swim, into the nearby lake, then stoned him to death.”
It is claimed the teenage suspect planned to give her sister's boy to Catia Rabelo, 35, who reportedly needed a child as she had told her partner she was pregnant.
The child was later found in the care of Rabelo's 15-year-old son, reports say.
Rabelo had fled the scene by the time the baby was discovered, although she was later arrested, The Sun reports.
She has allegedly confessed to inciting the youngsters to take part in her child snatching plan.
The baby has been taken to hospital and is in a stable condition despite the brutal nature of his birth.
