The victim was found at a Salvation Army senior living complex in the 3000 block of Orange Street around 2:40 a.m. when authorities were asked to do a welfare check on an elderly woman living there.
Officers responded and found the woman inside with visible injuries. She was pronounced dead at the scene.
A short time later nearby officers detained an individual they suspect to be connected with the homicide.
"We had other officers in the area," said Riverside Officer Ryan Railsback. "Once they found out we had a possible murder victim, they contacted a subject who was on foot walking in the area. Based on some evidence, they believe that subject is linked to this homicide investigation."
The identity of the man has not been released. Authorities say he has no known connection with the victim or the facility. A possible motive remains under investigation.