While I applaud your willingness to help someone in distress, your story is a good illustration of the fact that situations are not always what they initially appear to be.
Bingo. This point was emphasized in each of my CHL classes--initial and refresher.
LEOs often consider DV scenarios among the most hazardous they encounter.
As much as we all want to believe that we are "the good guy", the people directly involved in the situation may have an entirely different perspective, or, more likely, have zero objectivity.
To clarify: I'm not saying that you shouldn't get involved. That is a decision only you can make. IMHO, this world needs all the "good guys" it can get.
Unfortunately, you will likely have to make that decision in an instant, under difficult circumstances.
Just as making the decision to carry involves some introspection, I am asking you to reflect on this before you are "in the moment". Make up your own mind up under what parameters you will insert yourself into the situation.
I understand that the variables are almost infinite, and as a result, setting up an "if: then" logic tree is impossible.
So what you really need to consider is the macro scale.
Yeah, easier said than done, I know. If it were easy, anyone could do it. The problem is, most of us never even think about it until it happens to them...and it's hard to be objective when tensions are high.