As a Swiss I have never heard about this but it does sound very interesting. Do you have any sources for this?
https://taxjustice.net/2017/06/02/whistleblower-ruedi-elmer-...
There was also the case of Eckart Seith. He was very recently acquitted probably because the issue gained too much attention to cover it up. He was accused of economic espionage and other crimes. The prosecutor very clearly was partial and only after 5 attempts he was dismissed.
This isn't restricted to Switzerland at all of course, similar problems are as prevalent in other countries if you look closer.
As glad as I am to be born and living in Switzerland, it makes me sad to see how much BS my country does in the background, be it banking, resource industry like Glencore, food industry like Nestle etc. And due to our small size it seems like not many scandals leak or come to light, not even internally.
Of course Credit Suisse and UBS get slapped with fines almost every year it seems, but that feels more like a show than anything more.
I don't know anything about this case and it doesn't seem plausible that anyone had him killed. But the release of panama papers did also lead to the sudden death of a few people.