405 ILCS 5/3-606

A peace officer may take a person into custody and transport him to a mental health facility when the peace officer has reasonable grounds to believe that the person is subject to involuntary admission on an inpatient basis and in need of immediate hospitalization to protect such person or others from physical harm. Upon arrival at the facility, the peace officer may complete the petition under Section 3-601. If the petition is not completed by the peace officer transporting the person, the transporting officer's name, badge number, and employer shall be included in the petition as a potential witness as provided in Section 3-601 of this Chapter.