Mass. Gen. Laws ch. 39, § 11: Persons authorized to call meetings upon resignation of selectmen

Section 11. If a majority of the selectmen or any less number shall vacate their offices, or if the full number shall fail to be elected or qualified, the selectmen in office may call a town meeting. If there are no remaining selectmen, the town clerk may call it; and, if there is no town clerk, a justice of the peace may call it in the manner prescribed in the following section.