Subject to this section, the Secretary shall commence proceedings under § 19-408 of this subtitle on the Secretary’s own complaint or on a complaint made to the Secretary by any person. A complaint shall: be in writing; be signed by the complainant; and state specifically the facts on which the complaint is based. If a complaint is made by any person other than the Secretary the complaint shall be made under oath by the person who submits the complaint. On receipt of a complaint that alleges facts that are grounds for action under § 19-408 of this subtitle, the Secretary shall appoint an officer of the Department of State Police, with the rank of lieutenant or above, as the investigating officer for the complaint. The investigating officer may assign responsibility for conducting the investigation to other members of the Department of State Police. On conclusion of the investigation, the investigating officer shall determine whether there is a reasonable basis to believe that there are grounds for disciplinary action under § 19-408 of this subtitle. If the investigating officer finds a reasonable basis as provided under paragraph (1) of this subsection, the Secretary shall act on the complaint as provided under § 19-410 of this subtitle.