The SIU is investigating after a boy's jaw was allegedly broken during his arrest by Toronto Police.

Police say the arrest came as they were on pro-active patrol near Yonge St & Gould St Sunday night.

While talking to a group in a laneway, officers noticed a boy among them was showing characteristics of being armed.  Turns out, the 16-year-old was holding a loaded 9mm handgun.

The boy faces 8 gun-related charges.  He can't be named under the Youth Criminal Justice Act.

Ontario's Special Investigations Unit steps in when someone is hurt or killed during an interaction with police.