The shooting happened in an apartment building in the 1100 block of 8th Avenue S.W. in May. (CBC)

Calgary police were justified in shooting a man wielding a knife in an apartment building in May, an independent probe has concluded.

Criminal charges will not be laid against police constables in the non-fatal shooting, Cliff Purvis, executive director of the Alberta Serious Incident Response Team, said on Tuesday.

Four officers responded to a 911 call about a man being held at knifepoint in the downtown complex in the 1100 block of Eighth Avenue S.W. on May 26.

A man with a 20-centimetre knife confronted police in a hallway of the building and refused to comply with several requests to put the knife down. He continued to approach officers, said Purvis.

As the man came within about 1.5 metres of the officers, a constable shot him once with a rifle, said Purvis. The bullet went through the man's arm, into his stomach and out through his back.

The man was taken to hospital with non-life threatening injuries, and has fully recovered. He co-operated with the investigation, which concluded that he made the original 911 call.

"ASIRT's investigation revealed the man was suffering from a mental illness. The executive director of ASIRT has reviewed the file and has concluded the actions of the police officers were justified in the circumstances," said an ASIRT statement.

ASIRT is an independent civilian agency that looks into police actions that result in death or serious injury.

The apartment building where the shooting happened is run by an agency that provides affordable housing for people with mental illness and special needs.