Both men were living in the Polson Special Care Facility — a secure facility at the Vernon Jubilee Hospital that provides care for people who have dementia complicated by psychiatric and behavioral issues.
Vernon RCMP says the victim died on the scene of his injuries.
Interior Health has begun an internal investigation, but has not released either of the men's names.
SFU gerontology researcher Charmaine Spencer says the criminal justice system is ill-equipped to deal with offenders with suffering from serious dementia.
"In most cases when these occur, the person is cognitively impaired, has absolutely no idea what they've done or the harm they've caused," said Spencer.
With files from the CBC's Brady Strachan. You can follow him on twitter @BradyStrachan