“Chief (Eric) Larsen asked the FBI to look at it,” police Lt. Joseph Nosalik told CNN on Wednesday.
Video of the incident in the cafeteria shows a fight begin between two students as the officer, working school security at the time, attempts to break it up before either being hit or falling backward with one of the students. It appears he hits his head on the edge of a nearby table.
The 12-year-old girl is eventually handcuffed, picked up and led away, the video shows.
Pete Deates, president of the Kenosha Professional Police Association, said Wednesday the union welcomes “any outside agency to investigate and examine our actions.”
The girl is currently receiving counseling and psychiatric services and undergoing physical therapy, her family attorney Drew DeVinney told CNN on Tuesday.
No decision has been announced on whether either of the girls involved in the fight will face charges.
CNN’s Brad Parks contributed to this report.