Provincial Police have released the name of the person killed in the horrible crash on the 401 westbound, east of Thickson Road near Whitby.
29 year old Manu Goswami from Scarborough, was sitting in the back seat of a Toyota Corolla, when it was rear-ended by a transport truck around 10:30 on Tuesday morning.
Goswami was killed and two others, a 29 year old man from Scarborough and a 47 year old man from Scarborough were sent to hospital with serious injuries.
A person in a third car was also sent to hospital.
Police aren't sure why the transport rammed the back of the Toyota, but say the investigation continues.
The driver of the truck wasn't hurt.