@Chengdong0
I am not saying not irritating to your business. I am just speaking from experience.
Unless the mentally ill person is a danger to himself or someone else. The police can only treat it has a trespassing complaint. If he isn't on the property no they ill not look for a trespasser. If he is on the property they have to respect his rights also. They ask him to leave and don't do it again.
In this type of scenario, and I don't blame your guests I would be scared also. Try reaching out to a church or charity that assists the mentally ill. They have resources and experience creating solutions that work for the mentally challenged person. Ideas we just don't think of maybe a gift of a pair of socks to the man might accomplish what an expensive fence doesn't. Someone trained as to evaluate his situation