Things to ask yourself before injecting yourself into a violent situation that doesn't directly involve yourself.
Are they a threat to me?
Are they a threat to my loved ones?
Are they a threat to my property?
Can you subdue with restraint legally one or more of the said attackers and do I have the right to do so?
If you do subdue the attacker, are you prepared for possible other attacks on yourself from others in vicinity.
Are you prepared for legal ramifications and explaining why you involved yourself in a dispute best handled by law enforcement. Not only to the police but judges and court system aswell.
Are you prepared for not only criminal charges to be pressed against you but civil aswell?$$$$$

Best to call 911.
If someone is attacking a visibly weaker (child, woman) and you come to aid, you still have liabilities, but they will be looked at differently. Also coming to the aid of a law enforcement officer will be looked at differently.
Just some things to think about in this day and age before you try to play hero. Two dipshits beating each other to death may be just what karma has worked out for them.
JMO