Peter Roy Brooks, 72, was arrested late Wednesday at the Wexford Seniors Residence Long Term Care facility near Lawrence Avenue East and Pharmacy Avenue in Toronto's east end.
The 72-year-old woman who died after the assault late Wednesday has been identified by Toronto police as Joycelyn Dickson.
A 91-year-old woman, who has not been identified, was taken to hospital with non-life-threatening injuries.
All three people involved lived at the residence located at 1860 Lawrence Ave. E., Toronto police said.
Det. Sgt. Wayne Banks said it was an isolated incident.
"We believe that there is only one person involved in this incident … That person is in custody. So again, for the tenants of the building and for the community, there's nobody that's outstanding or at large."
Brooks was scheduled to appear in a Toronto court Thursday afternoon.
Police said they received multiple 911 calls from the residence at about 11:15 p.m. ET on Wednesday. Officers arrived at the home and found both women with "obvious signs of injuries."
The 72-year-old woman was pronounced dead at the scene.
Police said a weapon was used in the attack but would not say what it was.
CBC News reporter Linda Ward was at the scene on Thursday morning and said relatives of the injured 91-year-old arrived shortly after the assault happened.
"Her family arrived on scene in time to jump into the ambulance with her," Ward reported.
Matthias Jetleb, whose mother lives in the long-term care facility, said the home has a problem with understaffing.
"I'm concerned that this may have been something that sort of highlights that, because, really, I have to ask how two people could be assaulted without someone stepping in?" he told CBC News.