Quebec's police watchdog is investigating a shooting at the courthouse in Maniwaki, Que., in which an 18-year-old man was seriously injured when he was shot by a special constable.

The Bureau des Enquêtes Indépendantes (BEI), which investigates incidents involving law enforcement officers, said there was an altercation between the man and a special constable around 1 p.m. ET.

According to a BEI news release, the teenager seized a baton from the special constable during the altercation and hit him with it. The investigation is ongoing, but the statement said the special constable then fired his gun, shooting the man in the head.

Police say 2 people were seriously injured at the Maniwaki, Que., courthouse. (Florence Ngué-No / Radio-Canada)

An officer with the Sûreté du Québec (SQ) said both suffered serious injuries and have been taken to the hospital, though the extent of their injuries is still unclear.

The identities of the injured have not been released.

Special constables in Quebec are sworn peace officers who work in courthouses and other government buildings. Because the incident involved one of the constables, it falls under the jurisdiction of the BEI, which has a mandate similar to that of Ontario's Special Investigations Unit.

A witness to the incident posted a video on social media appearing to show the scuffle between the constable and the 18-year-old prior to the shot being fired.

In it, people in the room can be heard saying, "Put down your gun." Others can be heard appealing for calm in both English and French.

Earlier this afternoon, witnesses reported a heavy police presence at the building, which sits at 266 Notre Dame St. in Maniwaki, about 135 kilometres north of Ottawa.