How do I deal with my FIL who has undergone severe behavior changes: sexual inappropriateness, random spending, etc.?

My father-in-law has had two or three minor strokes over the past three years, and his wife passed away a year and a half ago. He has since become increasingly erratic in his behavior. He sends money to mail scams, he is sexually inappropriate with almost any female he comes in contact with nurses, neighbors, friends, etc.