The gun laws made sense 200 years ago, of course they did. You needed a gun to protect your family and property. Nowadays this is simply not the case- the police force are more than happy to enforce justice on your behalf, and the Second Amendment seemingly leads to more harm than good.
But if Ms Rivett had a lover and if she was sharing that lover with somebody else, then it puts quite a different complexion on the whole murder. Suddenly, we now have not only a motive but also a mystery man in the house.