An Oklahoma mother has been arrested after she failed to report the rape of her 6-year-old daughter, police said. The most twisted part of the story: The rapist was her 11-year-old brother, according to authorities.

Both mother and son were arrested Friday afternoon after a worker from the Department of Human Services got a tip about the supposed assault and began to interview members of the family, NewsOk reported.

The Daily Mail obtained a police report about the incident, where the victim told the child welfare worker she had been doing homework in her room on Wednesday when her brother and a 7-year-old cousin asked her to take off her pants.

Once she had removed her bottoms, the girl said both her cousin and her brother put “their things in her and it hurt,' the police report states. The victim also told police her mother said not to tell anyone about the sexual abuse.

None of the suspects or witnesses have been named in order to protect the identity of the victim, the Daily Mail wrote.

The mother admitted to DHS workers she was aware of the incident and chose not to report it, but added that her son placed on the blame on his younger cousin.

The brother was placed under arrest on a charge of rape in the first degree after officers interviewed him at his house on Friday.

Authorities also talked to his older sister, who said she learned about the abuse Thursday, the day after it happened.

“She stated she was getting ready for work on [Thursday] and heard [the victim and her brother] arguing,” the police report stated. When the sister asked them what they were arguing about, her brother claimed that their cousin assaulted their little sister.

He told her the cousin pulled down the young girl’s pants and “touched [her] with his penis but did not penetrate.”

According to the brother, he told his cousin to leave because he was mad that his cousin “touched her with his penis” but the cousin returned. The brother didn’t admit to anything innapropriate and only said he kissed his sister on the cheek, but that his cousins were “telling kids what we did.”

When the older sister called her mother to let her know what had happened, she found out she already knew but didn’t understand why she hadn’t called authorities.

The mother was arrested for failing to report child abuse, and the 6-year-old girl was brought to the hospital and has been placed in protective custody.