I think maybe you don’t know lawyers very well. A good samaritan law won’t prevent a lawsuit from going forward if the contention also exists that the good samaritan was the primary cause of death, to wit: bullets from his gun.
What, by the way, is really crude stuff?
BTW, you can sue anyone about anything you want at any time in any court.
There are lawyers who are happy to do so. Most of them would prefer to win so sometimes they'll talk you out of it ~ 'cause they don't see a chance for a fee