VAUGHAN, Ont. -- A 28-year-old woman and her dog are dead after they were struck by a car while walking on a sidewalk in Vaughan, north of Toronto.

Police say the pedestrian and her pet were struck while on the sidewalk (on Thornhill Woods Drive north of Summeridge Drive) around 8:15 p.m. Monday.

Police are investigating why the 2011 Lexus sedan crossed the roadway and mounted the curb before the collision.

They say the Vaughan woman and her dog were struck from behind and died at the scene, while the car also hit several trees and a hydro box before ending up on its roof.

The vehicle's driver, an 84-year-old woman, and her passenger, an 88-year-old man, both of Vaughan, were taken to hospital with minor injuries.

Police say the investigation is in its early stages and they have not laid any charges.