The vehicle was turned away from him. From his own footage, it is obvious he could see that. And it was going very slowly. We know from his final comment, '****ing bitch', why he did it. He was wound up and angry. Those two women would have annoyed me as well. But that is no reason to kill someone.
What do you think about him holding his gun in one hand whilst filming with his phone with the other hand. Is that professional. Also, the rule is that, even if he is in mortal danger, he can only shoot if there is unable to get out of the way. A simple step to the right would have avoided all this. So, following their own rules, he is guilty.
This is the definition of serious bodily harm:
In the US, serious bodily harm (often referred to as serious bodily injury) is a legal term defined across federal and state laws as a physical injury that involves a substantial risk of death, protracted and obvious disfigurement, or a protracted loss or impairment of the function of a bodily member, organ, or mental faculty.
Even if he was clipped by her bumper at 2mph, that comes nowhere close to meeting the definition.
The second two shots at point blank range into her head, after she had actually passed him, were obviously illegal.