Not the Onion

There is precedent.

Something similar happened for a man who killed a Christian Science practitioner for forbidding him from taking his son to the doctor despite getting medical care himself.

This had been done after he tried to have said practitioner charged with negligent homicide and voluntary manslaughter charges over what became of the kid. The Justice System let him walk because of religious exemption, the father took revenge himself and the Jury decided that the man was merely correcting an error made by the Judge of that case.

Disclaimer: Christian Science is neither science nor Christian. It was basically a clickbait name given to a Quantum Mysticism cult that existed before Quantum Physics was really a thing. Please do not "Skydaddy" it up like a common redditor in response.

Does this count as murder? https://www.history.com/news/the-original-wild-west-showdown-bill-hickok-davis-tutt

He got arrested after killing someone and the jury found him not guilty with a lot of witnesses seeing the act.