Officers responded to reports of a stabbing at about 2:30 a.m. at Rumors Nightclub and Lounge on Andrew Street, according to Sgt. Alain Tremblay.
The 32-year-old victim was from the Listuguj First Nation reserve in Quebec. He was taken to a local hospital with a perforated lung.
Tremblay believes the victim has since been airlifted to a Montreal hospital.
A 17-year-old male also from the reserve was arrested at the scene.
No charges have been laid, but Tremblay said he believes it was not a random incident.