The initial communication should outline the complaint, advise the suspect of their rights, outline the process which will be followed, and tell them what the next steps shall be (e.g.):
This communication DOES NOT CONSTITUTE a formal statement of charges. The next steps shall require the Commander, upon consultation with relevant authority, to determine whether these matters rise to a level requiring formal discipline, what charges, if any, shall be proffered, and what level of formal process is appropriate to resolving the matter in the best interests of the Service. The Commanding Officer has the authority to suspend the volunteer from service pending formal proceedings (or for up to two weeks) and is taking that authority under advisement.
In the background, the officer should start the process of gathering information about the complaint and building a record. Remember at this point that the suspect's confidentiality should be preserved where possible. The possibility of Undue Influence (RsMO 40.126) shall specifically be avoided:
Undue Influence: any statement made by a superior officer which might prejudice their subordinates against the accused. In other words, if the Commander says to the Chief of Staff, "He's guilty and he needs to be punished for it," that is undue influence.
Types of Proceeding
Next, a meeting must be conducted to determine what level of discipline to pursue.