Officers from Knox Highway Patrol are investigating a serious injury collision that occurred in Boronia on Wednesday afternoon, 10 November.
Investigators have been told an emergency response vehicle was stopped on the southbound emergency lane on Eastlink about 3.30pm.
The driver was assisting a motorist who had come to a stop on the freeway after he discovered his vehicle, a red Nissan SUV, had a flat tyre.
The occupants of the car with the flat tyre were standing on the side of the road when a white Ford wagon crashed into the rear of the emergency response truck.
The force of the collision caused the emergency response truck to crash into a 56-year-old Clyde North man who was standing beside the vehicle, the Nissan and a 65-year-old Chelsea Heights man who was changing the flat tyre.
The Clyde North man was taken to hospital with non-life-threatening injuries and the other man received minor injuries.
The driver of the Ford, a 43-year-old Cranbourne East man, along with two passengers in his vehicle at the time of the collision, were all taken to hospital.
The rear seat passenger, a 45-year-old Cranbourne East man, received life-threatening injuries.
The exact cause is being investigated and officers are appealing for anyone who saw the white Ford wagon travelling southbound on Eastlink prior to the collision or with dashcam footage, to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au
