Perhaps PRB should consider retaining the services of a company like Shareholder Intelligence Services to monitor trading for suspicious activity.

http://www.shareintel.com/newwhatwedo.cfm

ShareIntel provides public companies with robust, 24/7, secure-password-protected web access to dynamic, customized, and modifiable shareholder and broker-dealer transaction analytics. Instant interpretation is produced both numerically and graphically via proprietary analytic tools. This is intended to enable management to effectively identify, interpret and communicate shareholder and broker-dealer movement to the market. In addition, predetermined proprietary filters and queries trigger timely email alerts to inform management of relevant or unusual trading activity, thereby prompting logical action- steps to be taken by the Company and its CEO and its trusted advisors (i.e., investment bankers, legal counsel, investment relation professionals) to protect market capitalization.