B.C.'s Independent Investigations Office and Vancouver police are calling on witnesses to an officer-involved shooting in a busy SkyTrain station during Monday morning's rush hour to come forward.

The plea comes as new video has emerged of the frightening moments before the police altercation leading up to the shooting at the 29th Avenue station in East Vancouver. An officer from the Vancouver Police Department shot a man they say was armed with a machete after he allegedly threatened passengers on a busy train.

Transit Police responded after receiving reports of an armed man, and called in VPD as backup.

Officers managed to barricade the man inside a SkyTrain car, but he broke his way out using the knife, according to VPD.

Video taken on the platform shows the armed man on the SkyTrain as several passengers hurry out an adjacent door, while officers point their weapons.

Afterwards, the man wanders up a flight of stairs carrying a knife. Officers told him to drop the weapon several times, and he was shot after he didn't oblige, says the VPD.

The scene played out in front of dozens of passengers.

The man was taken to hospital, where he remains. Although the IIO said he was in critical condition, the VPD said he is in serious yet stable condition and expected to survive.

Police have identified the man, but say his name will not be released until criminal charges are laid.

Anyone who saw, heard or recorded the incident is asked to call the IIO witness line at 1-855-446-8477, or the VPD Major Crime Section at 604-717-2541.