Section 72. The commission may appoint and remove a secretary. It may expend for such investigators, clerical and other assistants as may be necessary for the performance of its duties such amounts as may be appropriated and the employees shall retain all collective bargaining and other rights previously held. The commissioner may appoint a chief investigator and other investigators, who shall be exempt from chapter 31, for the purpose of enforcing or causing to be enforced the penalties provided by law against every person who is guilty of a violation of chapter 138 of which they can obtain reasonable proof, and shall make all necessary and appropriate investigations for that purpose. Each person appointed as an investigator shall complete a basic reserve police officer training course through the criminal justice training council and shall attend a basic training course conducted by the commission. All investigators shall attend an annual in-service training course pursuant to this section. Each member of the commission, and each of its employees having access to moneys received by it, shall give to the treasurer a bond for the faithful performance of his duties in a penal sum and with sureties approved by the treasurer.