I have 2 girls, we don't have guns or toy weapons in the house, we don't watch things that are violent and we don't encourage it - they still have managed somehow to turn their elbows, toys and anything else into "killing swords" or guns to fight each other! They pretend to be dead and then drag each other around - the first time it was quite disturbing but talking to other mums it is something that other kids do too. They never hurt each other but just use their imagination. Hopefully they will grow out of it but in the meantime I emphasise the being being gentle and kind to each other and not hurting each other in the process.