In that video, we dont see everything that happened. When he was initially slapped, did he run straight to the weapon and get it? Or did he simply try to flee, and only went for the rod after he saw them chase him behind the counter. Its also hard to tell exactly how the initial blows happened once he'd gotten the rod. Did the women still attack first, behind the counter? Did the woman's movements once she was on the ground appear to be threatening (including reaching into her coat, as if for a gun or knife)? How much longer did the beating occur after the end of this video? These things may seem like splitting hairs, but they will be important in court.
Just because some woman is yelling for him to stop, or even someone trying to take the weapon away, that's not legal grounds that he must stop 'defending himself'. If he gets a good lawyer, and can make the 'felt in fear for his life' defense stick, he can probably sway at least one juror with reasonable doubt. The key is getting a good lawyer, which sadly and ironically depends on how much publicity the media gives to this event.
Or, since he was working at McDonalds, he might have just wanted to go back to prison.