The Special Investigations Unit (SIU) say 27-year-old Martin Gordyn of Niagara died on Tuesday in a shooting involving police near the Niagara Parkway.
Niagara police also say two of its officers were hurt with minor injuries and a woman was arrested at the scene.
Officers say they responded to reports of a suspected impaired driver on Tuesday afternoon near Lundy's Lane and Corwin Avenue.
Roughly an hour later, they found a vehicle near Line 3 and the Niagara River Parkway.
The SIU says there was an interaction between police and Gordyn near a trail, "and the SIU believes there were a pair of bicyclists who witnessed that interaction."
That's when police shot Gordyn. He was taken to hospital with life-threatening injuries, but didn't survive.
The post-mortem is scheduled for Wednesday morning, the SIU says.