Family members told the Maywood Police Department they could not find or contact 35-year-old Sergio Brown or 73-year-old Myrtle Brown on Saturday.
Police filed a missing person report and searched the area. Officers found Myrtle unresponsive near a creek behind her home.
Myrtle's body was later taken to the Cook County Medical Examiner's Office. Her death is being investigated as a homicide, police said.
Police are still searching for Sergio, and asked anyone with information to call Maywood Police Investigations' Dennis Diaz at 708-368-4131 or the Maywood Police Department's anonymous tip line at 708-450-1787.