A gun purchased in the US for $500 "can easily sell for up to $5,000 in Canada", Norman Proctor, a Toronto Police inspector, said at a news conference last year.
The issue surfaced after Canada introduced stricter gun laws a few years ago in response to the 2020 mass shooting in Nova Scotia - the country's deadliest - in which 22 people were killed. The law included a ban on "assault-style weapons".
Some questioned the effectiveness of the ban, as the perpetrator was found to have obtained his guns illegally - three were smuggled across the US border from Houlton, Maine.
Once these American guns cross the border into Canada, police say they are frequently distributed across the country and used in violent crimes, like robberies, carjackings and homicides.
Chief Fordy told the BBC that in 2023, 90% of handguns recovered after violent crimes in Ontario - Canada's most populous province - were traced back to the US.
"Through our tracing and analysis, we know the top states (these guns come from) are Ohio, Texas, Florida and Georgia, in that order," Chief Fordy said.
Some are stolen, while others are bought using straw purchasers - an individual who buys a gun for someone who is not authorised to own it.
"Sometimes they are purchased in bulk, then sold here on the street for a handsome return on investment," Chief Fordy said.