Police are continuing to search for a youth who threatened an officer with a knife in Chesterfield - then ran away.
The crime happened on Alexandra Road West shortly before 3pm on Saturday when a police officer conducted a stop and search on a teenage boy.
He threatened the officer with a knife before running off.
A Derbyshire Constabulary spokesman said: "Firearms officers and the police helicopter were deployed to the area to conduct a search.
"However, the male was not located.
"The youth is described as white, of a slim build, between 16 to 18-years-old and was wearing a black waterproof jacket with the hood up, dark coloured jogging bottoms and had a black rucksack on his back.
"Anyone with information is asked to contact us on 101, quoting reference number 18000134367."
This afternoon, the spokesman said the youth had still not been found.
Residents have expressed their shock and concern over the incident.
Concerns over youngsters' behaviour
The crime happened after Chesterfield police voiced concerns about youngsters acting anti-socially and being abusive in the town.
One 15-year-old girl recently spat at a security guard at the town's library.
Chesterfield PCSO Adele Chapman-Jones said: "We've had a number of reports recently about the behaviour of some large groups of secondary school children, between the ages of 12 and 18, who are acting anti-socially, being abusive and volatile.
"Our team has also recently dealt with a 15-year-old girl who spat at a security guard. This kind of behaviour won't be tolerated.
"People should be able to visit, shop and work in our town without the worry of being subject to anti-social behaviour and we are working hard alongside partnership agencies to help ensure Chesterfield continues to be a safe place to be."
PCSO Chapman-Jones added: "Parents may be able to help us prevent these issues by simply taking the time to find out where their child is, who they are with and what they are doing - and by making sure they understand what is anti-social and unacceptable behaviour."