Benzos work. They lower anxiety and do so by creating a sense of apathy -- you are too relaxed to care about being anxious about anything. An offshoot of that is that you can become so apathetic that they also loser inhibitions.
There are many documented cases of benzos leading to violence. Which sort of makes sense -- if you reach that stage of apathy the conditioning than prevents you from becoming violent slips away.
But, frankly, in my worst benzo days, while I have been sorely embarrassed by my behavior, I would have never hit a soul. His Xanax and booze are reducing his inhibitions to reveal just what might lie underneath -- a dude who hits a woman. Run run run run run.....