Provincial police say one person was sent to hospital with 'life altering' injuries, after a collision at Highway 48 and Stouffville Road.
Sgt Dave Woodford says the original collision involved 2 vehicles in the intersection.
He says one of the drivers got out to inspect the damage, when other vehicles couldn't stop or avoid the incident, coming into contact with the vehicles.
That's when the person was struck.
They've been sent to Sunnybrook hospital, with what Woodford calls potentially life threatening injuries.
A second person was taken to hospital with minor injuries.
In all 7 vehicles were involved.