The 11-year-old, whose name has not been released, has been transported to a juvenile facility where she was booked on a charge of second-degree murder, according to the Edmond Police Department.
The child was arrested around 1 a.m. on Thursday, according to police.
"We recognize this is a heartbreaking situation for the family involved. Our thoughts are with them as they grieve this tragedy," Edmond police said in a statement.
Police said they would not release any identifying information about the incident since it involves juveniles.
The mother, who was not at the scene of the shooting, told investigators her daughter called her saying someone shot her son, according to a Broadcastify recording of Edmond Police and Fire.
The teen suffered a gunshot wound to the head, according to Broadcastify.