Aside from calling the police, which should be done even if it's just so that there is an official record of the steps you've already taken should things get worse later on...
I don't know where you are in the world, but here in the UK there are reasonable expectations all landlords are held to, which include things such as building safety/security and to deal with any other tenants causing a disturbance/breaking the law.
We have specific teams within the local council who investigate accusations that these expectations aren't being met (my ex landlord was investigated for years, but there were never enough tenants prepared to back up the claims, and they were very complex issues needing evidence like you couldn't imagine!) and they can be stripped of their control of their own properties should things reach a certain point, with various options offered like time to improve the situation, training courses, or sale of the property to someone else.
If the expectations aren't being met, the case can be made that the contract is void and therefore there is nothing to break, you are free to leave as you wish.
As I said, I've no idea if any of the above applies where you are, but regardless, records of everything need to be kept, with any evidence you can possibly gather (difficult in the case of harassment unless it becomes physical or involves letters/graffiti) police records, copies of any/all letters sent to building management and the likes... Everything you can get to support that you've done everything by the book and the situation hasn't been resolved.