trailer park management

I manage a trailer park and some of my tenants have lived here for nearly twenty years. The majority of them are seniors. However, I am having a problem with one of the tenants have a son whom just got out of prison and while he was gone, I managed to evict all the problem tenants, put in surveillance cameras, and pretty much keep all the gang bangers and drug addicts from coming around. Unfortunatley, this one person's son has an aquaintance that I informed they weren't allowed back on the property, he is allowing that person to come around again. This is after I spoke to him and advised him to not let this person on the premises for any reason. My other tenants have asked me to keep this person away also. There is nothing but problems when this person is around. It's difficult to get any information from the local police here. I cannot get a restraining order if I don't know this person's full name. Can anyone give me some advice or even a suggestion on how to deal with this situation???????