UPDATED 02/15/12 7:21 a.m.

OAK PARK, Ill. (CBS) – An 80-year-old man with Alzheimer’s disease was beaten to death at an Oak Park nursing home and police said Tuesday it appears another resident is to blame.

As CBS 2′s Pamela Jones reports, Oak Park police said Tuesday that they were still investigating the fatal beating of Anibal Calderon, 80, at the Oak Park Healthcare Center, located at 625 N. Harlem Av. in Oak Park.

A nurse found the man unconscious Sunday night in the nursing home’s Alzheimer’s and dementia ward. He was taken to Rush Oak Park Hospital and later transferred to Rush University Medical Center, where he died early Tuesday.

Police believe another resident at the nursing home, a 66-year-old man, beat Calderon in the head with something.

Police think Calderon got into an argument with the other resident, and the 66-year-old ended it with the beating.

An autopsy on Tuesday determined Calderon died from craniocerebral injuries and blunt trauma from an assault. The death was ruled a homicide, according to the Cook County Medical Examiner’s office.

LISTEN: WBBM Newsradio’s Bernie Tafoya reports