The man who was shot by police following an altercation at an anti-racism rally in downtown Calgary on Saturday attacked the officer with a pipe, according to the body that investigates officer-involved shootings.

The Alberta Serious Incident Response Team (ASIRT) said officers radioed a description of the 30-year-old man after he showed up at the rally, yelled at attendees and then fled when police approached.

A nearby officer with three recruits in his patrol car heard the description and spotted the man.

That officer, who police say has seven years experience with CPS, followed the man and pulled his cruiser in front of him.

Police blocked off the scene in the 100 block of Seventh Avenue S.E., in the alley behind the Palomino. (Jeret Holt/CBC)

With the recruits following at a distance, the officer tailed the suspect into the alley.

"There was brief physical contact," said ASIRT executive director Susan Hughson, "we do know the officer drew his baton which was recovered on scene."

The man produced a metal pipe and within seconds the officer drew his gun and shot him.

The officer also suffered injuries and was treated at the scene according to police.

"Men and women who are in law enforcement have a very difficult and challenging task that can be violent," said Calgary Police Chief Paul Cook, "they have to rely on their training they have to rely on split second decisions to preserve their life or to preserve the life of others."

'Very agitated, very angry'

Sherry Walford was taking photographs downtown when she saw a man approach the rally near city hall.

"All of a sudden, I see a crowd gather and this guy walks by and he starts yelling out 'white power' and then starts swearing at these guys and fingering them," she said.

Jason Devine, an organizer of Anti-Racist Action Calgary's 8th annual rally, said the man looked agitated and angry.

"Racism is a form of violence and people who are racist tend to be very angry and tend to carry out acts of violence," said Devine.

Devine said police later returned to the rally to take statements from the crowd.

The man remains in intensive care in hospital and is listed in critical condition.

This is the second officer-involved shooting in Calgary in less than a week. On Monday, Anthony Heffernan, 27, was killed after an altercation with police in a northeast Calgary motel room.

The Alberta Serious Incident Response Team investigates incidents involving serious injury or death that may be attributed by the actions of a police officer. ASIRT is asking for anyone with information to call 403-592-4306.