Well, first, did a plan exist? Communication to participants is an essential part of establishment of a plan. If not, then there may be tax fraud, depending on how contributions were dealt with. If a plan did exist, misuse of employee benefit plan assets is a FEDERAL felony (and Ill look for the cite).
In either event, I would 1) advise them of the error of their ways; 2) resign immediately, and 3) consult an attorney about your obligations concerning having witnesses/having information/evidence of the commission of a crime.
Part of me also would also anonymously alert the DOL (their website lets you do that) about this situation (and I resist that urge almost daily....)