Well, not a lawyer, but does not seem like an accident to me. And I am not perfect, but we should not just draw and shoot at anything that startles us.
Sad situation no matter how it goes down.
Saw a news report on it this morning which had additional details. They soft pedaled it in the article but a few hours earlier he had a confrontation where someone (not named) threatened him and trying to beat down his front door. His back yard was fenced so when someone was pounding on his back door, inside his fenced yard, and then hiding and jumping out at him… well, he was primed to defend himself.
Sad situation but really why would you do that? I blame the prevalence of the practical joke shows and videos… you know the ones where they set up a situation to scare the holy bejesus out of some family member… yeah, not funny. In this case, tragically not funny.