Ubiquitin & Avi & whoever else it’s relevant to: While you are correct that one is mechalel Shabbos even for Safeik pikuach nefesh, it has to be a certain level of safeik. This came up once in another thread a while back. I think someone raised the possibility that if you see a lost purse on Shabbos, because there might be medicine in the purse that the person will die if he doesn’t have, so therefore it ‘s a safeik pikuach nefesh.
Obviously, that is a very small safeik so we are not mechalel Shabbos. There are halachos regarding how big a safeik has to be in order to be considered safeik pikuach nefesh. We don’t call a doctor on Shabbos every time that someone is sick.
Likewise, there are halachos regarding a situation like this. That is why we have poskim. If you don’t trust your Rav, ask another one. But it requires a psak halacha. And no one here is qualified to give it since we don’t know the situation.
And Ubiquitin, as I pointed out before, the OP said that he has no idea if this is something that requires police intervention. In his last post, he wrote that he doesn’t know that there is physical violence going on. It is entirely possible that he is the nervous type.
It shouldn’t take any more time to call a recognized poseik than it does to get advice from anonymous posters. And you will feel more at peace if you know that you asked Daas Torah and are following halacha.