Many years ago , when my daughters were about 11 and 15, and my (then) husband was drinking more and more heavily, he came back from the pub and started an argument. I was standing in the kitchen doorway and can't really remember what exactly happened but I ended up lying on the floor. I think he probably made some threatening gesture and I reacted and lost my balance. I wasn't hurt, but for the first and only time, I felt that we couldn't stay in the house with him and ended up with the three of us staying in a neighbours house overnight. Nothing like that ever happened again, probably because I made it very plain it would not be tolerated. I must have talked it through with the girls, but can't really remember the details now.
We divorced a few years later, and he moved a long way away.
Many years even later, when younger daughter was in her 30s, some conversation caused her to comment that her father had been violent' to me. Verbally yes, - often - but physically, only the once.
I'm telling you this because obviously the incident had a far greater impact than I had realised. Whether the fact that she now has mental health problems is in any way related to what she saw as a child, I do not know.
I do now know that maybe I should have talked far more about the incident with the girls, or even sought professional advice. But as it was a 'one off' I didn't.
So please, - you must at the very least talk to your son . But I really think that the whole incident needs to be discussed with the whole family and explained. If they can't do that then maybe you should seek help elsewhere.