To suspend such a young child for fashioning a gun out of a pastry is quite ridiculous but just demonstrates the heightened tension that exists in schools. This can only have a detrimental effect on the children. In any school that I have worked in until very recently the child would have been fixed with a withering look and told he was a very silly boy. The other children would have stifled giggles and that would have been the end of the matter. The other case is much more serious. A child who threatens to shoot another is being exposed to too much violence in society. This may easily be through unsuitable television programmes, careless talk by the adults around them etc.
A seven year old hasn't reached the age of discretion, they do not understand that we often speak figuratively and they understand only on a literal level. This head teacher was trying to discover whether it would be possible for the child to have access to a gun in the interest of the safety of the whole school. The parent needs to sit the child down and tell them she/he is very upset and disappointed in this behaviour. It is totally unacceptable to threaten anyone in any way. If the child has concerns about another's behaviour the correct thing to do is to speak to the teacher. Please take this seriously and don't take the attitude that it is your child just mouthing off. A sharp reprimand now, and some determined effort to exclude violence, even in the form of video games/television, may save your child and yourself from a lot of heartache.