Who goes alone in a home-made submarine with a strange mad scientist?
So maybe that's what happened? He talked the journalist into something and later saw that she had died because of that, probably also causing harm to the submarine?, then panic'ed and told lies to the police.
I would definitely have gone on a tour of that submarine with him.
Not a scene of crimes typically investigated, prosecuted, etc. We'll never really know what crimes would get on the books if the criminal justice system decided (against their better judgement) to go after the powerful as hard as they go after the weak.
I gave it an up vote in order to unbury the rest of the discussion.
There isn't. Mental illness is only a very weak predictor of violence.