Winnipeg police were called to the Osborne Street Bridge for a report of an injured man.
They arrived to find a 28-year-old man suffering significant trauma to his upper body.
He was rushed to hospital in critical condition. As of Sunday afternoon, police say he remains in hospital.
Police say they do not have any more information on the situation and are asking residents in the area for help.
The Major Crimes Unit asks anyone who may have been walking or driving in the area around 5:30 A.M. to reach out to police.
Those with potential surveillance footage or drivers with dash cam footage are being urged to contact investigators.
Police were called to the 600 block of Brandon Avenue around 5 A.M.
Upon arrival, they found a 57-year-old man who suffered a minor injury.
Officers believe the suspect approached a 54-year-old transit driver who was sitting in his parked vehicle and shattered the driver-side window.
The driver waved down a passing transit bus for help. A passenger on that bus, an off-duty transit worker, went to help and he was assaulted.
Neither man required attention. The suspect fled before police arrived.
The investigation is ongoing.