The Alberta Serious Incident Response Team has begun its investigation into the actions of a Calgary Police Service member who fired his service weapon during the apprehension of a knife-wielding suspect.

On Saturday afternoon, police were called to the Marlborough LRT station following reports a man with a knife has been causing a disturbance.

A CPS member conducting a patrol of the area located a man matching the description of the suspect hiding behind a dumpster outside Marlborough Mall. The officer approached the man and the suspect fled on foot into the Sears department store.

Inside the store, the suspect produced a large machete and the officer countered by deploying his conducted energy weapon at the man. The countermeasure proved ineffective.

"As the officer retreated and attempted to draw his service weapon, the man came at the officer and struck the officer with the machete causing significant and severe injury," explained Sue Houston, ASIRT executive director. "The officer fired his service weapon and the man was struck and fell to the ground."

The officer was transported to the Foothills Medical Centre by ambulance. The unnamed member of the Calgary Police Service remains in hospital in serious but stable condition.

The suspect, a 20-year-old man, was transported to hospital in critical, life threatening conditon where he underwent emergency surgery.

"The machete was recovered at the scene and found to have been recently purchased," said Houston.

The blade of the machete is 48.3 cm long.

"Any officer-involved shooting is considered a serious incident and, as such, will be thoroughly investigated to determine whether the use of possible lethal force is lawful and justified in any given case."

Surveillance camera footage of the incident within the Sears store is being reviewed by ASIRT.