1. Ask any cop and he will tell you that a DV is the riskiest, most potentially explosive call out you can go to; if you dont have to get involved, dont. The female could actually have become an attacker if you intervened.

2. Having a pistol, as somebody mentioned, makes getting involved much dicier. Not only must you have lethal force justification, but even getting into a non-lethal force fight is dangerous because of gun retention issues.