The man killed in Sunday's multi-vehicle crash on B.C.'s Coquihalla Highway had stopped to help victims of an initial collision, according to police.

Mounties said Highway 5 was closed for around 10 hours after the collision, which happened just after 12:30 p.m. PT near Larson Hill, about 30 kilometres south of Merritt. 

A 35-year-old man from the Lower Mainland, who has yet to be identified, had stopped to help in the initial crash when he was struck and killed by another vehicle.

A 78-year-old man from Kamloops was airlifted from the scene with critical injuries. Police say his condition had improved by Monday.

Two other people were taken to hospital with minor injuries.

RCMP say investigators believe the collision was caused by speed relative to road conditions and sudden changes in road conditions.

A total of six vehicles were involved in the crash, which closed the northbound lane of the highway.

With files from the Canadian Press