York Regional Police investigators are appealing for witnesses to come forward after a collision between a pickup truck and a cyclist in East Gwillimbury on Wednesday.
Police were called to the area of Doane Road, east of Warden Avenue, shortly before noon.
The vehicles were travelling in opposite directions when they collided.
Police say the cyclist – a 58-year-old man from Markham – was taken to hospital with serious, life-threatening injuries. The driver of the pickup truck remained on scene.
The investigation is ongoing.
Any witnesses who have not spoken to police yet or anyone who may have dashcam footage from the are around the time of the collision can contact police.