"A two-year-old child and a man have been killed in a head-on collision which has left the child's parents fighting for their lives.
The high-speed crash happened in Hamelin Way, Torquay, Devon, at about 2.45pm on Friday.
A black Vauxhall Vectra driven by a Polish man in his 20s collided with the car, carrying the family of three from Ireland, between Gallows Gate and Kerswell Gardens.
A spokesman for Devon and Cornwall police said the mother and father remained in a "critical, life-threatening condition" in hospital and police were working to contact their next of kin.
The incident was witnessed by a police officer who was on the scene.
All four occupants of the cars were taken by air and land ambulances to Torbay hospital in Torquay and Derriford hospital in Plymouth.
The driver of the Vauxhall Vectra was arrested before being taken to hospital, where he subsequently died.
Police family liaison officers are with the family of the man, who lived in Torquay.
Paul Netherton, Assistant Chief Constable of Devon and Cornwall police, described the incident as "extremely traumatic".
He added that the adverse weather conditions being experienced throughout the country did not contribute to the cause of the collision.
The road remained closed on Friday night while the vehicles were recovered and forensic examinations took place.
Netherton added: "This was an extremely traumatic incident where emergency services were working on the family at the scene and subsequently in ambulances and at the hospital.
"It was a head-on collision at speed. The black Vectra was coming down the hill and appears to have swerved into the path of the oncoming car.
"The members of the family are in a critical, life-threatening condition in Derriford and Torbay hospitals.
"We are trying to identify their next of kin in southern Ireland to inform them, and the next of kin for the gentleman who has died have been informed and our thoughts are obviously with the families involved at this time.
"The road does remain closed and there is an ongoing investigation and recovery of all the forensic material in the vehicles etc, which will be going on all night."
Netherton said because the driver of a police car witnessed the crash, the force has referred the matter to the Independent Police Complaints Commission as a matter of course. The officer's police car had not been pursuing the vehicles.
Any witnesses are asked to call police on 101 and quote log 0405 of 6 July."