So, Joe's being held without bail. The prosecutor railed, "You don't bring a gun to a fistfight and gut-shoot someone!", and "He shot him in the stomach... he gut-shot him!"
Having known Joe for over a dozen years, and knowing him to be extremely non-aggressive, I'll go out on a limb and say that he didn't know he was in a fight until the other driver punched him in the face. (Which is deadly force, BTW, and warrants deadly force in response.) Joe's a small guy, maybe 5'5". He had all three of his kids in the car with him. If it had been anything other than a "wow, just had an accident, let's pull over" in his mind, I believe he would have sped away from an aggressor.
I could be wrong, of course. But it wouldn't be the Joe that I know to do anything else except use force only in response to an unexpected attack. This is someone who was among the first five guests in my NH home after we moved, delivered our first load of bio-logs, and has stayed in our travel trailer. He's had full access to our house any time he came to visit.
Unless he's made a change (something he doesn't do easily), I can even tell you that he was carrying an HK squeeze-cocker (I forget which variant) in a black leather thumb-break holster at 3:00.
Also: just in case this comes up later, Joe and his late wife were polyamorous. I mention this only because an early version of the Valley News report apparently said the other driver's wife first called in that "My boyfriend shot my husband." That version wasn't archived, but a mutual friend quoted it on FB. That shouldn't change any legitimacy to the use of force. Joe's poly nature actually reinforces my opinion that he wasn't the aggressor, because mutual consent was part of his core nature.