I think short of some global mass causality event (Nukes etc), any likely event will be short lived (how short is another question); but I feel pretty confident it will end and after it does there will be some reckonings for any otherwise extra lawful incidents. It may be explainable why you shot looters in your neighborhood; but shooting them at long range might be harder. You might be able to explain why you took groceries or building materials or fuel; but using violence to take them will be even harder.
Perhaps the best definition of SHTF is intentionally vague because those scenarios are predictably unpredictable. Plan for the worst