I don't see the overreaction. She went outside when she heard her dog barking, presumably to see why and stop it. It wasn't a toy gun either - it was an imitation rifle.
Do you honestly think it's okay to point imitation firearms at people or animals in a public place, or anywhere for that matter? Could you tell the difference between an imitation rifle and a real one when some nutter is pointing it in your direction and shouting threats at you?
The only problem here is the sentence was suspended - he should have been locked up.