A man with an imitation firearm who had a gun pointed at him at the back of a bus by armed police has been given a conditional caution, it has emerged.

The man, in his 20s, got on the number 21 First bus - which was full of passengers - at Theatre Street, Norwich, but was arrested after firearms officers boarded and pointed a gun at the suspect who was found at the back of the top deck.

A huge police presence attended the incident at about 10.30pm on Thursday April 12 after staff at Tesco Express alerted officers.

Eastern Daily Press: Tesco Express, London Street, NorwichTesco Express, London Street, Norwich (Image: Submitted)A man had accidentally dropped a handgun in the London Street store after becoming aggressive when they refused to serve him as he did not have ID.

The man, who left shop assistants "terrified", walked out with two friends but was tracked to the top deck of the Bowthorpe-bound bus by firearms officers.

He was arrested - along with two others - on suspicion of being in possession of a firearm by police who seized the weapon which was said to be a BB gun.

A Norfolk Police spokesman said the man in his 20s, who is from Norwich, has been given a conditional caution after he admitted possessing an imitation firearm in a public place, as well as possession of cannabis.

The spokesman said an 18-year-old and a teenage boy also arrested will "face no further action".

Eastern Daily Press: Police in Theatre Street, NorwichPolice in Theatre Street, Norwich (Image: Submitted)A conditional caution issued by police is an alternative to prosecution in certain cases, which may be relatively minor, but where the offender must admit the offence and comply with certain conditions.

If conditions are not complied with, and there is no reasonable excuse, a prosecution may be commenced for the original offence.

Eastern Daily Press: Police in Theatre Street, NorwichPolice in Theatre Street, Norwich (Image: Submitted)The incident alarmed a number of people who were out in the city at the time.

One eye witness said: "I was absolutely shocked to see it, I felt so sorry for the poor bus driver and all the passengers."