The Police Ombudsman's Office has appealed for witnesses to an incident during which a 13-year-old boy was arrested in Banbridge on Saturday evening (2 March).
It happened at around 7pm in the Solitude Park area of the town, near the Tesco supermarket.
A spokesman said: "Some footage of the arrest has been posted on social media and we are also examining police body worn video of the incident.
"However, we would also be keen to hear from anyone who saw what happened or who may have recorded other footage on their mobile phones.
"Anyone who believes they may be able to assist is asked to contact the Police Ombudsman's freephone witness appeal line, which is 0800 032 7880."