Armed officers were sent to a Sheffield city centre car park when two youths were spotted with guns by members of the public.
When officers arrived on Arundel Gate they found two teenage boys – aged 15 and 16 – carrying weapons, but on closer inspection found them to be BB guns.
Now police chiefs have warned against the dangers of BB and imitation guns.
Chief Inspector Caroline Rollitt, of South Yorkshire Police, said: “Firearms officers are highly trained and experienced in dealing with all types of firearms incidents.
However, it is always difficult to assess whether someone is holding a viable or an imitation firearm.
“Consequently, officers will always assume the firearm is viable and will react accordingly to the potential threat.
“This summer, when the firearms support group attend any incidents of anti-social behaviour air weapon use, they will also be trying to inform young people and their parents about the dangers of handling air weapons, especially in public places such as fields and woods, and the offences that they may actually be committing.
“Only too often, we hear of tragic accidents where children have lost their lives after being shot by an air weapon, yet if parents are still intent on buying air weapons for their children, they need to ensure they are supervised at all times and they need to be fully aware of the dangers that they pose.”
Armed officers visit schools across the county delivering a presentation warning about the dangers of guns and knives.
n Anyone with information about those with access to firearms should call police on 101.