The Buddha did not actually arise for the purpose of teaching about good & bad kamma. The teaching about good & bad kamma is merely a 'secondary' teaching in Buddhism. These kinds of questions that create worry, flurry & anxiety in the mind about trivial matters are not the purpose of Buddhism. Buddhism exists to set the mind and people free (rather than place people into bondage from making mountains out of molehills).
As an example, recently Hillary Clinton lost the US presidential election. In her previous terms in government, Hillary Clinton voted for every foreign war resolution & is said to be personally responsible for the destruction of the good nation of Libya. Despite her complicity in the deaths, murders & raping of millions of men, women & children, when Hillary Clinton lost the election, scores of fully ordained Western bhikkhus (monks) & bhikkhunis (nuns) were grieving her loss (such as here).
This example shows how individuals in general, including fully ordained monks & nuns, are indirectly supporting evils infinitely more evil than the killing of a mouse by a cat (which is not actually evil since the laws of kamma only apply to people rather than to animals). If the laws of kamma operated in such a indirect manner, these pro-Clinton monks & nuns would probably all end up in the hotttest & most torturous Avīci Hell for eons & eons.