A 22-year-old policeman from Wiltshire has been killed when his patrol car left the road and hit a tree.
Pc Daniel Cooper, who was described as highly regarded and popular, died at the scene of the accident near Bradford-on-Avon on Monday evening.
The trained police driver was responding to a call to help other officers dealing with an incident.
"Paramedics were called but Pc Cooper sustained very serious injuries and sadly died," a police spokesman said.
Ch Insp Hedley said the loss of Pc Cooper's life was tragic.
"Dan was a highly regarded and popular young officer who was just at the start of his police career," he said.
"His family have been told and they have requested no flowers be left at the roadside.
"As a mark of respect force flags will be flown at half mast."
Ch Insp Steve Hedley added that an investigation to find out why his car left the road was under way.
The Health and Safety Executive and the Independent Police Complaints Commission have been informed.
Wiltshire Police said the officer was driving the marked car along Westwood Road towards Trowbridge when the crash happened at about 2000 GMT.
It is believed he lost control on a left-hand bend and left the road before hitting the tree.
Anyone who saw the car was asked to contact police.