Sounds like a financial crime to me, and by filing you are confirming suspicion, not that you are specifically aware of what's happening.
I think you'd have a lot harder time justifying why you didn't file when the beneficiaries find out and want to sue that you will justifying why you should file.
As far as what you could consider it, I would think perhaps fraud could be considered, embezzlement, misuse of position (maybe?), and/or the always helpful Transaction with no apparent economic, business, or lawful purpose.
Some of those might be a stretch, but I'm sure others could offer opinions on them as well.
In summary, I would file.
Someone's about to get horned!