A policeman who was threatened with a sawn-off shotgun by a teenager in Berkshire said he was shocked when he realised the youngster was armed.
Pc John Wildridge was on patrol in Slough in February when he stopped to speak to 16-year-old Dan Danila.
When the teenager fled, the officer followed, but the boy pulled out a gun.
Danila is now serving four years in jail for possessing a firearm with intent to endanger life and for making threats to a police officer.
He was sentenced at Reading Crown Court on 28 May.
The drama began when the officer pulled up in Tesco car park, near Slough train station, on Sunday 28 February, shortly after 0000 BST.
Instead of speaking to the officer, the boy ran off towards the bus station, so the officer followed on foot.
Pc Wildridge said: "At first I didn't realise that the lad had a gun.
"I just thought he was trying to avoid speaking to me for some reason and I was shocked - it's not the sort of thing you expect to happen in Slough.
"I just calmly stepped away and used my radio to contact the control room for help.
"After I took four or five steps back, the boy turned and started to run away from me.
"It was shortly after this that he went into the bus station and discharged the gun, although fortunately no-one was injured and he was arrested by some of my colleagues soon after."
The 35-year-old Thames Valley Police officer said his fiance, who is also in the force, heard the drama unfold over the police radio system.
"For a few minutes [she] thought that I'd been shot," he said.
"It wasn't until I was back at the police station having a cup of coffee that it began to sink in what had happened.
"Although thankfully I wasn't harmed, I honestly feel that the situation could have been a fatal one if it wasn't for the quick response of my colleagues."
The officer, who has been with the force for six years, said he has had trouble sleeping since the incident.
He said: "I must admit that I have been left with all kinds of feelings about what I went through on that night.
"I tend to spend a lot of my free time going over the incident again and again in my head."