Police say 80-year-old Anibal Calderon was beaten Sunday and died from his injuries Tuesday.
He was a resident at Oak Park Health Care on North Harlem and suffered from Alzheimer's.
Police say he may have been hurt in a fight with a fellow patient.
An autopsy revealed Calderon died from blunt head trauma.
A nurse found Calderon unconscious about 8:40 p.m. Sunday in the Alzheimer/dementia ward. Paramedics took Calderon from the extended care facility to Rush Oak Park Hospital, police said. He was later transferred to Rush University Medical Center, where he was declared dead at 1:01 a.m. Tuesday, according to the Cook County Medical Examiner's office.
Police said Calderon was injured in an altercation with a 66-year-old patient.
Oak Park police are still investigating.
The Sun-Times Media Wire contributed to this report.