When to fear someone with Paranoid schizophrenia?

my brother in law is, and on top of his meds, he is also a severe drug user and alcoholic, and thinks that me and my children are a threat to him because my husband his brother, does not get drunk and take care of him like he thinks kris should. he only lives 2 min walk away he is always going through the yard, urinating in the yard in front of the house and beating on the front door all the time, we have tried to call the cops and we have also tried to get kris and freds mom to take over guardianship with fred but she tells us to just deal with it and get used to it . i dont want to see anything bad happen to fred just get him the help he needs how