Being a witness to domestic abuse in New York or anywhere can be extremely upsetting. Not to mention, it can leave many of us wondering if we should just mind our own business. However, staying silent about domestic abuse is tantamount to tacit approval of it. If you believe that you have witnessed domestic abuse, according to breakthesilencedv.org, you should never assume that somebody else will report it.
Probably the most obvious response is to call the police. You can do so anonymously if you wish, and this is likely the best course of action if you believe that the abuser is violent or dangerous. Additionally, this is a good road to take if you believe that you are hearing an abusive altercation but are not around to directly witness it.
If the abuse is taking place in a public arena, consider taking out your cell phone and recording it if at all possible. This may result in securing hard evidence against the abuser.
If you know the victim at all, and you are in public, you can try to approach under the guise of being excited to see the victim; this may deescalate the situation for the time being. If at all possible, you can offer to help the victim, but only do this if you are not within earshot of the abuser. If you are male and the victim is female with a male abuser, it is probably better not to approach at all.
It is never a good idea to try to physically intervene if the abuser is being openly violent. You cannot know if the abuser will instead turn around and become violent with you, or if the abuser is armed.