He was apparently very contentious about the submarine and his history with others involved in it as well.

I could see an escalating scenario where she, as a reporter would, started questioning around that topic. She hits the right buttons, and he loses it and injures her badly enough that he now has to make a decision.

Sounds like a reasonable hypothesis to me, taking in mind the many sources talking about his short-tempered character.

Fortunately glamour or statistics are not relevant in justice, only truth and proven facts. At the current moment there is zero data available supporting the mobster hypothesis... but also zero data (unless policemen know something more) supporting the hypothesis of a sexual crime or a rape.

Is a murder, pretty obviously, but the reason of the murder is unclosed still. All possibilities are open.