The Special Investigations Unit is investigating after Chatham-Kent police used a firearm during an altercation in Tilbury on Sunday.
The police service was called to the community around 10:50 p.m. to respond to a report of a man who was armed and in distress.
"Upon arrival, an altercation ensued which resulted in the male being shot by police," the police service said in a media release on Monday.
Officers administered first aid, then the man was sent to hospital to be treated for life-threatening injuries.
The SIU is an independent agency that investigates serious injuries, deaths and allegations of sexual assault involving police.