Yeah see this is why i don't give people i don't know that well my details - all i can really suggest is you ask him to stop contacting you and redirect his messages to your spam folder. If he gets threatening contact the police and let them handle it. Hope this gets resolved swiftly, all the best.

*EDIT* sorry i didn't realise this wasn't a new situation - again i would just make sure that none of his messages reach you and sadly theres nothing you can really do about living near him other than move which is something i hope you don't have to resort too. Im not sure whether you can apply for a restraining order so all i can really suggest is that you speak to your local police office and see what they advise. Again, hope you manage to get this resolved soon.