TULSA, Okla. (KFOR) – Authorities are continuing to investigate after a girl in Tulsa allegedly stabbed her younger brother last week.

Late Thursday night, Tulsa Police were called to a reported stabbing in the southern portion of the city. When officers arrived at the scene, paramedics and firefighters were already performing CPR on a 9-year-old boy, police explained in a press release.

The child was rushed to the hospital but later died from his injuries, Tulsa Police said.

According to investigators, the boy’s 12-year-old sister woke up her parents, who had been upstairs, and said that she had stabbed her 9-year-old brother.

The 12-year-old girl was taken into custody and is being held at the Family Center for Juvenile Justice. Police said the agency’s Child Crisis Unit is now handling the investigation.

Police told KOTV they are still working to determine why the girl stabbed her brother.

Neither child has been identified by police.