Retreat. Observe. Report. That's my motto in this situation.
If the fight comes to you, do your best to get away - but be prepared to defend yourself.
This is the best reaction. Their problems are not your problems and their emergency is not your emergency. Too many unknown variables to get involved in someone else's fight, argument, etc.
Even if it's a lady, old man, or child. You can play good citizen / hero if you want but you better be prepared to pay the consequences.