How to handle an abuse situation?

I wanted to share this and ask for your thoughts.

We are told that men should do more.  If you see something DO something.  So I was at a major train station and trying to eat some food before travelling home.

Two people came up.  I wasn't paying attention so I don't know if they came together or one followed the other.

Shortly after the male started abusing the female.  Verbally.  He stood up over her and was threatening and intimidating.  She was in tears and obviously scared.  He didn't hit her but he shoved his face down into hers and made it impossible for her to stand up or leave.

I won't go into all the details of what was said but it was clear that he was controlling and possessive and was really angry that she had talked to another man in a shop.

One comment she made was "I don't want to marry you any more".

This went on for fifteen minutes. Now I am 70 years old and I am wearing a back brace due to breaking a vertebra.  I couldn't take on someone a third my age and far larger.

I looked for any help but no one else paid it any attention.  I couldn't find police or security.  It didn't seem to be an emergency in that no physical force was being used.  So dialling "000" (our equivalent to 911) seemed unwarranted.

The question is "what could I or should I have done"?  What processes exist to deal with violence in a relationship?  We are told that "violence against women and children is wrong" and that we should do more. 

But where is the support for that?