I think that guy was gauging what was going on before he made up his mind. To be fair, unless they were beating the ever living shit out of her and she's already beaten to a pulp or unconscious, how do you know what transpired before they started fighting? You're basically walking in on two people having their own drama and you're third wheeling. I would say start recording as soon as you see something is off then if shit is getting too intense for some "money" problem then split them up.