I think he understood in that
exact precise moment the gravity of the situation he was in and the "publicness" of it all, so he tried to remove himself immediately.
Again it is clear from all the evidence that was presented in the trial that this was a toxic relationship. Whilst it's easier to manage such situation behind closed doors, he was first tussling with her in the car so there's the driver as one independent witness to the dynamics of the relationship . Then he was hoisting her into the car which was again captured on street cctv so further eyeballs on your relationship.
Also given (in my opinion) she is a alcohol dependent, unstable woman and didn't want to let up (evidenced by the fact that she was willing to turn trackstar with disregard for her own safety to incoming traffic, all in her pursuit of Majors), had he stayed with her either in the car or on the roadside, in what way was he going to win? He's a famous actor who happens to be black and brolic, and she's some lily white blondish woman. Passersby would have been watching, potentially interevening AND if they recognised who he was, then undoubtedly putting camera phones all in his face. He didn't want all that exposure because again she clearly wasn't going to let the situation go and resume it in a less public setting.