What you can do is threaten him with a possible set of suits based on these conditions:
1. Tortuous interference with a business
. As your agent and as your employee, he could not try to siphon of perspective employees and clients especially by using your own logo without authorization.
2. Trademark and Copyright infringement. By using your logo without permission, he violated your intellectual property rights (even if the trademark was never registered) and attempted to use your company trademark for his own profit. In addition, by building a website that was substantially similar to yours, he may have violated the copyrighted information on your website. Again, even if the copyright was never registered, you have protection from others taking your work on and passing it off as their own.
3. Possible defamation suit. You do not have to prove damages in defamation per se, when it deals with a person's livelyhood or business reputation. By spreading possible mis-truths, he may be liable to you for damages.
Taking legal action against him is your choice. What you can always do is threaten him with a cease and desist order, and if he doesn't comply, sue him under those three areas.
Please contact me if you need any further information.
Dimitry Alexander Kaplun, Esq.