405 ILCS 5/4-401
A petition for emergency admission may be submitted to the facility director of a facility by any interested person 18 years of age or older. The petition shall include a detailed statement of the basis for the assertion that the respondent meets the criteria of Section 4-400 including a description of any act or significant threat supporting the assertion; the name and address of the spouse, parent, guardian, and close relative or, if none, any known friend of the respondent; a statement of the petitioner's relationship to the respondent and interest in the matter; the name, address and phone number of any witness by which the facts asserted may be proved. The petition may be prepared by the facility director of a facility.
405 ILCS 5/4-401