I remember when I was taking care of an elderly relative, I noticed some things were coming up missing at his home. At first, he accused me of stealing from him, but I told him I wasn't that kind of person. I was just as concerned as he was about the thefts. I called a local elder law firm and asked someone there how to proceed.
He told me to set up surveillance equipment in the house, like a nanny cam or a stuffed animal with a camera inside. He also said I should make a list of everyone who has access to that house, especially relatives. It was a longer list than I thought. When I checked the cameras a week later, I saw his son take some cash out of a jar in the living room. I reported it to the local police and they later charged him with elder abuse for other things he did.