You need to report this to the EEOC, call an employment lawyer in your area and they will give you advice as to how to deal with this to gather evidence, witnesses and if you are in true fear of bodily harm, report this to the police. Get the name, address, telephone number and perhaps a photo of the people who are threatening you and give it to the EEOC and your attorney when you get one. You can get a free consultation with most attorneys.
Disclaimer: It is impossible to evaluate a legal problem without a comprehensive legal consultation and review of all the facts and documents at issue. Consequently, this response does not constitute or establish an attorney-client relationship but is offered for general informational purposes only. Laws differ from state to state and each case turns on facts specific to the case and parties thereto, thus this answer does not constitute legal advice, and should not be relied upon as anything more than a starting point or suggestion that the questioner seek professional assistance from a practitioner in your state or county/parish, practicing in your area of law.