It’s understandable that you were caught off guard. So, going forward, don’t have any communication again. From what I recall, from your previous posts, wasn’t this man abusive towards you?

Given how angry you are with yourself for talking to him, if he contacts you again just say you don’t want any further contact in future. Presumably he lives locally to you, which is how come he bumped into you, by chance?

It must be an awful situation to be in, but you don’t owe him anything. Remember that. You have zero obligation to this man. Keep strong and stay away.