The pensioner was declared dead at the scene, at Delamer House in Walton-on-the-Naze, Essex Police confirmed. A fellow residernt has been arrested on suspicion of murder.
Emergency services were called to the home just after 9am yesterday following reports that a woman had been seriously injured, police said. Officers and ambulance crews attended but the woman died.
Nearby resident John Knights said security was tight at the care home.
Retired financial adviser Mr Knights, whose wife Marlene runs the Bucket and Spade guest house a short distance from Delamer House, said: “My mother had to go into Delamer about two years ago and I can tell you that it was quite tricky to get in and out of there.
“Security was tight. You couldn’t just go up to the building and get in.
“You needed a security code to get in. It had electronic key pads on the door, so to get inside you needed to know those.
“Whoever was responsible must have known the code.”
A spokeswoman for the care home said there would be no comment until staff have spoken with police.