He was an arrogant d!ck long before I knew his politics. That aside though,
1. He took on the role of producer in addition to actor and it's my opinion THAT makes him more responsible for what happens on both sides of that gun.
2. Instead of owning up to firing the gun, even accidentally toward her or in her direction he goes on national TV with George Snuggleupmypuss and proclaims he never touched the trigger. I feel a lot of actors would have at least said " you know what ,I was told to pull the trigger, I did, and now this whole thing is a terrible tragedy/accident.
I feel like his multiple roles make him the main fall guy in this case. Unless I heard it wrong there are suppose to be a crew of 3 on the set when weapons are involved and he cut 1 out due to budget. That's as good as saying "we could have been safer but I wanted to cut corners".