40 ILCS 5/5-113

"Act of duty": Any act of police duty inherently involving special risk, not ordinarily assumed by a citizen in the ordinary walks of life, imposed on a policeman by the statutes of this State or by the ordinances or police regulations of the city in which this Article is in effect or by a special assignment; or any act of heroism performed in the city having for its direct purpose the saving of the life or property of a person other than the policeman.