Charge him all you like, you will just wind up with an acquittal.... He’s not guilty of murder or even manslaughter.
He’s a idiot, but he’s not going to face serious charges, unless some other piece of information were to come out, like HE KNEW when he pulled the trigger it had a live round in it... Otherwise, nope.
He’s a douchebag, but his actions in this are not remotely criminal murder or manslaughter.
I know he is not guilty of murder. Neither are the two examples I cited.