It doesn't matter where you are, until you do something about it it will just continue to get worse. For the amount of money that landlord profits they should be paying for a security guard...especially after getting hit multiple times. They would lose so fast in a court battle vs the tenants for not allowing them to break their contract too.

I'd be popping them in the face with a pellet gun from the bushes or the roof. Unless you were caught in the act there is no way anyone would trace a pellet back to you.