A 16-year-old boy is facing nine criminal charges after drivers on Highway 401 in the east end of Toronto saw a young man in a pickup truck shooting at passing vehicles on Sunday.

Ontario Provincial Police said Monday that witnesses reported seeing a young man firing what appeared to be an assault rifle on Sunday at about 4:30 p.m. ET. He was leaning out of the passenger side of the truck, they said.

The incident occurred in the westbound collector lanes of Highway 401 near Port Union Road just west of Pickering, Ont.

Police said they located the vehicle, a 2008 Dodge pickup truck, and found the weapon was actually a paintball gun, air-powered, that was designed to look like an assault rifle.

OPP Sgt. Cam Woolley said Monday the incident frightened drivers on Canada's busiest highway. Drivers slammed on the brakes to avoid being hit.

"The callers were terrified. All available OPP units, as well as Toronto Police Emergency Task Force, were alerted and dispatched. The suspect vehicle was quickly located," Woolley said.

The 16-year-old, who can't be named under the Youth Criminal Justice Act, faces such charges as mischief endangering life, assault with a weapon and weapons dangerous to the public.

Woolley said charges may be laid against the driver of the truck.

Police are asking witnesses to the incident to call the OPP Toronto detachment.