Lender met Borrower on the street, demanded that Borrower pay a debt owed to Lender, and threatened to punch Borrower in the nose. A fight ensued between them. Mann came upon the scene just as Lender was about to kick Borrower in the head. Noting that Lender was getting the better of the fight, Mann pointed a gun at Lender and said, "Stop, or I'll shoot." If Lender asserts a claim against Mann based on assault, will Lender prevail?
Yes, because Mann threatened to use deadly force.  Yes, unless Mann was related to Borrower.  No, if it was apparent that Lender was about to inflict serious bodily harm upon Borrower.  No, because Lender was the original aggressor by threatening Borrower with a battery