A boy of 12 was killed when the car he was travelling in was involved in a smash with a police car.
The youngster died at the scene on Friday, despite attempts to save him.
He was a passenger in a red Peugeot 106 being driven south along the B2114 on Hammer Hill at Staplefield, near Haywards Heath, when the car was in collision with a marked police car travelling north just after 4pm.
The 18-year-old driver, who was from the Staplefield area, was taken to the Princess Royal Hospital in Haywards Heath, although his injuries were not thought to be life-threatening.
Chief Superintendent John Dransfield said: "We wish to express our sympathy to the family and friends of the boy.
"We are supporting all those who were involved in this crash and a road policing department family liaison officer has been with the boy's family.
"Police are appealing for witnesses to contact them."
The officers involved in the crash, who are based at Crawley police station, were not responding to a 999 call and were not engaged in a pursuit.
The driver of the Toyota Avensis police car, a constable in his 40s, and his passenger, a constable in his 30s, were taken to the Princess Royal with minor injuries but were later discharged.
The accident has been referred to the independent Police Complaints Authority.
Witnesses should call 0845 6070999.
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