First be clear that one cannot “have someone dismissed”. A manager, trustee, customer, fellow employee can request or even demand that an employee be disciplined. In that case, as in all matters of conduct and performance, the first step is an investigation. What happened? When? Who saw it? If the investigation shows that a disciplinary hearing is appropriate, then that is the next step–not because the trustee said so, or the customer demanded it, but because the facts require it.
Dismissal may or may not result, but that is up to the chairperson of the enquiry. The trustee will have to be called as a witness along with any other witnesses from the company and from the employee.