When you shoot somebody you have the obligation to render aid if they are still alive. Whether the deputies allowed the EMT's access or they did it themselves, the obligation was still there. Certainly if you as a citizen shoot somebody, you have an obligation to render aid unless you can't due to the wounded person still being a threat. It sounds like Yantis was totally incapacitated yet they evidently neither attempted aid themselves, or tried to get paramedics to. Nor did they allow his family to aid him. That's what the story is thus far.
I'm not sure I'd argue in favor of that.....
I'm not arguing. It's a known fact. If some dude breaks into your house and is raping your wife and you shoot him, you are supposed to render aid if he's not dead. Of course, if you're busy aiding your wife or if he still poses a threat to you, were you to help him, no such obligation exists. Feel free to disbelieve me and seek other sources of wisdom on this though.
